Power amplifier and communication unit

ABSTRACT

A power amplifier including: a first amplifier PA 2  having an input terminal and an output terminal; a passive circuit PC 3  having an input terminal and an output terminal; and a first switch SW 2  having a single-pole terminal and two multi-throw terminals, one of the multi-throw terminals of the first switch SW 2  being connected to the input terminal of the first amplifier PA 2  and the other of the multi-throw terminals of the first switch SW 2  being connected to the input terminal of the passive circuit PC 3 . This makes it possible to provide a power amplifier and a communication unit which can be operated with different frequencies, output powers or modulation types.

This is a division of application Ser. No. 08/849,355, filed Oct. 8,1997, now U.S. Pat. No. 6,111,459, which is the U.S. national stage ofPCT/JP96/02770, filed Sep. 25, 1996.

TECHNICAL FIELD

The present invention relates to a power amplifier and a communicationunit which process signals; at least one of the frequencies, the outputpowers and the modulation types of which are different from each other;and more particularly relates to a power amplifier and a communicationunit having at least one switch.

BACKGROUND ART

In recent years, various kinds of information communication units, suchas cellular phone units and portable information terminals, have beendeveloped or have just started to be commercialized all over the world.Each of these information communication units operates based on itsunique system. Thus, the frequency bands, the output powers and themodulation types are different from each other among these systems.Consequently, transmission power amplifiers adapted for the respectivesystems have been developed and integrated into the terminals.

In Japan, two types of communication methods are utilized for automobileradiotelephone units and cellular phone units, i.e., an analog type FM(frequency modulation) type and a digital type π/4 shift DQPSK(differential quadrature phase shift keying) type. Both of the analogand the digital types are assigned to the frequency band of 800 MHz,while only the digital type is assigned to the 1.5 GHz band.Furthermore, a cellular phone called “PHS” (personal handy-phone system)is for a digital type π/4 shift DQPSK type and the 1.9 GHz band. Theoutput power of automobile radiotelephone units and cellular phone unitsis on the order of 1 W, whereas that of cellular phones is on the orderof 10 mW. Since the former phone units have a cell radius of severalkilometers and a hand-over function, the phone units of the former typecan be used for communication even during travel in an automobile or thelike. On the other hand, the phone units of the latter type have a cellradius of several hundreds of meters and have been developed by such anapproach as to utilize conventional indoor-use cordless phone units foroutdoor use. Furthermore, though the 2.4 GHz band, i.e., the ISM(Industrial Scientific Medical) band, has been globally assigned toindustrial, scientific and medical applications, it is also underconsideration to apply the ISM band to wireless LANs (local areanetworks) within offices, factories or various kinds of sites inaccordance with the spread spectrum (SS) type so as to comply with thestandard in which the output power is 10 mW/MHz (frequency band: 26MHz). As can be seen from these tendencies, information communicationunits, which can be used anywhere at any time, will surely be popularfor use in daily life in the near future.

Conventionally, a transmission power amplifier satisfying the desiredfrequency band and the desired output power is integrated into thecorresponding terminal depending upon which of these types the terminalis based on. Thus, a user has been required either to have terminals ofdifferent types corresponding to the domestic service areas andapplications, or to buy an expensive, large-sized terminal compatiblewith several different types for itself.

FIG. 35 is a block diagram of a conventional example. This conventionalexample is a multi-stage power amplifier for transmitting two differentradio frequency (RF) signals having different frequency bands and outputpowers, in which two banks of power amplifiers corresponding to therespective frequency bands are used.

A first power amplifier PA1 includes: a first input matching circuitPA104; a first GaAs MESFET PA101; a first inter-stage matching circuitPA105; a second GaAs MESFET PA102; a second inter-stage matching circuitPA106; a third GaAs MESFET PA103; and a first output matching circuitPA107.

A second power amplifier PA2 includes: a second input matching circuitPA204; a fourth GaAs MESFET PA201; a third inter-stage matching circuitPA205; a fifth GaAs MESFET PA202; a fourth inter-stage matching circuitPA206; a sixth GaAs MESFET PA203; and a second output matching circuitPA207.

The power amplifier of this conventional example is surely compatiblewith different output powers, modulation types and frequency bands, butrequires a larger number of components for a single configuration. Thus,such a power amplifier is contrary to the recent requirement ofdownsizing a terminal and adversely increases the costs thereof.

FIG. 36 is a simplified circuit diagram of a radio frequency (RF)integrated circuit described in Japanese Laid-Open Patent PublicationNo. 8-88524 which was laid open (laid-open publication date: Apr. 2,1996) posterior to the priority date of the present application. Thispatent publication relates to an RF integrated circuit including anamplifier operating in both of analog and digital types. As shown inFIG. 36, the drain 3604 of an FET 3601 on the last stage of theamplifier is connected to the input terminal of an analog type outputmatching circuit PC1 and the input terminal of a digital type outputmatching circuit PC2 via a switch SW1. The output terminal of the analogtype output matching circuit PC1 and the output terminal of the digitaltype output matching circuit PC2 are connected to an output terminal3605 via a switch SW2. By switching the output matching circuits PC1 andPC2 and selecting one of them via the switches, the operationcorresponding to each type can be performed.

FIG. 37 shows a graph (a) showing the variations in distortion D andpower added efficiency η (i.e., the ratio of the difference between theinput RF power and the output RF power with respect to the DC powersupplied to an amplifier) with respect to an input power Pin and a graph(b) showing the variation in output power Pout with respect to the inputpower Pin.

FIG. 38 is a graph showing the input power dependences of the outputmatching circuits PC1 and PC2. The axis of the abscissas indicates theinput power Pin, while the axis of the ordinates indicates the outputpower Pout. Moreover, Pn denotes a nominal output power. In the regionwhere the output power varies linearly with respect to the input power,the distortion and the power added efficiency are low. On the otherhand, in the region where the output power varies non-linearly withrespect to a higher input power, the distortion and the power addedefficiency become high. In view of these characteristics, PC1 for theanalog type and PC2 for the digital type of the power amplifier areconfigured so as to have the RF power input/output characteristics shownin FIG. 38. More specifically, in operation, PC1 for the analog typedoes not require the linearity of the output power with respect to theinput power and is configured so as to have a high power addedefficiency (i.e., subjected to an efficiency matching). On the otherhand, PC2 for the digital type is configured so as to ensure thelinearity of the output power with respect to the input power (i.e.,subjected to a distortion matching) such that a distortion is notgenerated in an RF signal passing through the amplifier during theoperation. Then, the power added efficiency thereof becomes lower thanthat of the analog type.

Examining the disclosure of Japanese Laid-Open Patent Publication No.8-88524, the integrated circuit described therein can be regarded asbeing compatible with the analog and the digital signals in the samefrequency band (900 MHz) and with the same output power. Thus, in theabove-described integrated circuit, the output matching circuits PC1 andPC2 thereof are subjected to an impedance matching such that the loss ofa transmitted signal is minimized with respect to the same frequencyband. Therefore, in the case of transmitting RF signals in differentfrequency bands, the impedances cannot be matched with each other,thereby increasing the loss. As a result, the integrated circuit has aproblem in that a desired output power and a desired distortion cannotbe obtained in such a case. Furthermore, assume that the output powersare different from each other (e.g., a power on the order of 1 W and apower on the order of 100 mW are processed by PC1 and PC2,respectively). Then, in order to output a power on the order of 100 mWby using an active element capable of outputting a power on the order of1 W, a mechanism for controlling the input power of the FET isindispensable. If the active element is operated on the order of 100 mWby reducing the input power under such a control mechanism, then thepower added efficiency is extremely decreased as compared with theoperation on the order of 1 W, thereby adversely increasing the powerconsumption. As a result, when an information communication unit isdriven by a battery, the longevity of the battery is disadvantageouslyshortened. In addition, such a power amplifier is not compatible with RFsignals, the frequencies and the output powers of which are bothdifferent from each other. Furthermore, in case where such a poweramplifier is used as an integrated part of an information communicationunit having transmission and reception functions, some selection meansfor switching a signal to be transmitted by the power amplifier and asignal received via an antenna is required to be provided. Nevertheless,this point is not referred to in the above-cited patent publication. Inother words, the correlation between the transmission function of apower amplifier for switching the output matching circuits in accordancewith the analog and the digital types and the transmission/receptionfunctions of an information communication unit is not mentioned in theabove-cited patent publication.

In view of these problems, the present invention has objectives ofproviding a power amplifier which is commonly applicable to differentsystems used for various kinds of information communication units (i.e.,the systems having different frequency bands, output powers to betransmitted and modulation types) and can be formed in a reduced size atlower costs, and providing a highly value-added communication unit byusing such a power amplifier.

DISCLOSURE OF THE INVENTION

According to the present invention, a power amplifier is provided. Thepower amplifier includes: a first amplifier having an input terminal andan output terminal; a passive circuit having an input terminal and anoutput terminal; and a first switch having a single-pole terminal andtwo multi-throw terminals. In the power amplifier, one of themulti-throw terminals of the first switch is connected to the inputterminal of the first amplifier and the other of the multi-throwterminals of the first switch is connected to the input terminal of thepassive circuit.

In one embodiment, the power amplifier further includes a second switchhaving a single-pole terminal and two multi-throw terminals. One of themulti-throw terminals of the second switch is connected to the outputterminal of the first amplifier and the other of the multi-throwterminals of the second switch is connected to the output terminal ofthe passive circuit.

In another embodiment, the first amplifier includes discrete components.

In still another embodiment, the power amplifier further includes asecond amplifier having an input terminal and an output terminal. Thesingle-pole terminal of the first switch is connected to the outputterminal of the second amplifier.

In still another embodiment, a 3 dB band width of the second amplifierincludes a range from about 800 MHz to about 2.5 GHz.

In still another embodiment, gain characteristics of the secondamplifier include at least two peaks.

In still another embodiment, a first band which is a frequency rangecorresponding to a range from a first gain at a first peak of the gaincharacteristics of the second amplifier to −3 dB of the first gain,includes 1.5 GHz and, a second band which is a frequency rangecorresponding to a range from a second gain at a second peak of the gaincharacteristics of the second amplifier to −3 dB of the second gain,includes 1.9 GHz.

In still another embodiment, a first band which is a frequency rangecorresponding to a range from a first gain at a first peak of the gaincharacteristics of the second amplifier to −3 dB of the first gain,includes 900 MHz and, a second band which is a frequency rangecorresponding to a range from a second gain at a second peak of the gaincharacteristics of the second amplifier to −3 dB of the second gain,includes 1.9 GHz.

In still another embodiment, the first switch and the second amplifierare formed on one and the same semiconductor substrate.

In still another embodiment, the passive circuit is formed on thesemiconductor substrate.

In still another embodiment, the power amplifier further includes apower supply controller for controlling a power to be supplied to thefirst amplifier in response to switching of the first switch.

In still another embodiment, the first amplifier receives, amplifies andthen outputs an analog signal and the passive circuit receives andoutputs a digital signal.

In still another embodiment, the first amplifier receives and outputs afirst digital signal and the passive circuit receives and outputs asecond digital signal.

In still another embodiment, the first amplifier receives and outputs asignal having a first frequency and the passive circuit receives andoutputs a signal having a second frequency, the first frequency and thesecond frequency being different from each other.

In still another embodiment, the first amplifier outputs a signal havinga first output power, the passive circuit outputs a signal having asecond output power and a ratio of the first output power to the secondoutput power is equal to larger than 5.

According to another aspect of the present invention, a communicationunit is provided. The communication unit includes: a first amplifierhaving an input terminal and an output terminal; a passive circuithaving an input terminal and an output terminal; a first switch having asingle-pole terminal and two multi-throw terminals; a second switchhaving a single-pole terminal and two multi-throw terminals; a thirdswitch having a single-pole terminal and two multi-throw terminals; afront end circuit; and an antenna. In the communication unit, one of themulti-throw terminals of the first switch is connected to the inputterminal of the first amplifier and the other of the multi-throwterminals of the first switch is connected to the input terminal of thepassive circuit. One of the multi-throw terminals of the second switchis connected to the output terminal of the first amplifier and the otherof the multi-throw terminals of the second switch is connected to theoutput terminal of the passive circuit. One of the multi-throw terminalsof the third switch is connected to the single-pole terminal of thesecond switch, the other of the multi-throw terminals of the thirdswitch is connected to the front end circuit and the single-poleterminal of the third switch is connected to the antenna.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstamplifier having an input terminal and an output terminal; a passivecircuit having an input terminal and an output terminal; a first switchhaving a single-pole terminal and two multi-throw terminals; a firstantenna; and a second antenna. One of the multi-throw terminals of thefirst switch is connected to the input terminal of the first amplifierand the other of the multi-throw terminals of the first switch isconnected to the input terminal of the passive circuit. The outputterminal of the first amplifier is connected to the first antenna andthe output terminal of the second amplifier is connected to the secondantenna.

According to still another aspect of the present invention, a poweramplifier is provided. The power amplifier includes: a first amplifierhaving an input terminal and an output terminal; a second amplifierhaving an input terminal and an output terminal; and a first switchhaving a single-pole terminal and two multi-throw terminals. One of themulti-throw terminals of the first switch is connected to the inputterminal of the first amplifier and the other of the multi-throwterminals of the first switch is connected to the input terminal of thesecond amplifier.

In one embodiment, the power amplifier further includes a second switchhaving a single-pole terminal and two multi-throw terminals. One of themulti-throw terminals of the second switch is connected to the outputterminal of the first amplifier and the other of the multi-throwterminals of the second switch is connected to the output terminal ofthe second amplifier.

In another embodiment, the first amplifier and the second amplifierinclude discrete components.

In still another embodiment, the single-pole terminal of the firstswitch is connected to an output terminal of a third amplifier.

In still another embodiment, a 3 dB band width of the third amplifierincludes a range from about 800 MHz to about 2.5 GHz.

In still another embodiment, gain characteristics of the third amplifierinclude at least two peaks.

In still another embodiment, a first band which is a frequency rangecorresponding to a range from a first gain at a first peak of the gaincharacteristics of the third amplifier to −3 dB of the first gain,includes 1.5 GHz and, a second band which is a frequency rangecorresponding to a range from a second gain at a second peak of the gaincharacteristics of the third amplifier to −3 dB of the second gain,includes 1.9 GHz.

In still another embodiment, a first band which is a frequency rangecorresponding to a range from a first gain at a first peak of the gaincharacteristics of the third amplifier to −3 dB of the first gain,includes 900 MHz and, a second band which is a frequency rangecorresponding to a range from a second gain at a second peak of the gaincharacteristics of the third amplifier to −3 dB of the second gain,includes 1.9 GHz.

In still another embodiment, at least two of the first switch, thesecond switch, the first amplifier, the second amplifier and the thirdamplifier are formed on one and the same semiconductor substrate.

In still another embodiment, the second amplifier is formed on thesemiconductor substrate.

In still another embodiment, the power amplifier further includes apower supply controller for controlling a power to be supplied to atleast one of the first amplifier and the second amplifier in response toswitching of the first switch.

In still another embodiment, the first amplifier receives, amplifies andthen outputs an analog signal and the second amplifier receives,amplifies and then outputs a digital signal.

In still another embodiment, the first amplifier receives and outputs afirst digital signal and the second amplifier receives and outputs asecond digital signal.

In still another embodiment, the first amplifier receives and outputs asignal having a first frequency and the second amplifier receives andoutputs a signal having a second frequency, the first frequency and thesecond frequency being different from each other.

In still another embodiment, the first-amplifier outputs a signal havinga first output power, the second amplifier outputs a signal having asecond output power and a ratio of the first output power to the secondoutput power is equal to larger than 5.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstamplifier having an input terminal and an output terminal; a secondamplifier having an input terminal and an output terminal; a firstswitch having a single-pole terminal and two multi-throw terminals; asecond switch having a single-pole terminal and two multi-throwterminals; a third switch having a single-pole terminal and twomulti-throw terminals; a front end circuit; and an antenna. One of themulti-throw terminals of the first switch is connected to the inputterminal of the first amplifier and the other of the multi-throwterminals of the first switch is connected to the input terminal of thesecond amplifier. One of the multi-throw terminals of the second switchis connected to the output terminal of the first amplifier and the otherof the multi-throw terminals of the second switch is connected to theoutput terminal of the second amplifier. One of the multi-throwterminals of the third switch is connected to the single-pole terminalof the second switch, the other of the multi-throw terminals of thethird switch is connected to the front end circuit and the single-poleterminal of the third switch is connected to the antenna.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstamplifier having an input terminal and an output terminal; a secondamplifier having an input terminal and an output terminal; a firstswitch having a single-pole terminal and two multi-throw terminals; afirst antenna; and a second antenna. One of the multi-throw terminals ofthe first switch is connected to the input terminal of the firstamplifier and the other of the multi-throw terminals of the first switchis connected to the input terminal of the second amplifier. The outputterminal of the first amplifier is connected to the first antenna andthe output terminal of the second amplifier is connected to the secondantenna.

According to still another aspect of the present invention, a poweramplifier is provided. The power amplifier includes: a first passivecircuit having an input terminal and an output terminal; a secondpassive circuit having an input terminal and an output terminal; a firstswitch having a single-pole terminal and two multi-throw terminals; andan amplifier having an input terminal and an output terminal. One of themulti-throw terminals of the first switch is connected to the inputterminal of the first passive circuit, the other of the multi-throwterminals of the first switch is connected to the input terminal of thesecond passive circuit and the output terminal of the amplifier isconnected to the single-pole terminal of the first switch.

In one embodiment, the power amplifier further includes a second switchhaving a single-pole terminal and two multi-throw terminals. One of themulti-throw terminals of the second switch is connected to the outputterminal of the first passive circuit and the other of the multi-throwterminals of the second switch is connected to the output terminal ofthe second passive circuit.

In another embodiment, the amplifier includes discrete components.

In still another embodiment, a 3 dB band width of the amplifier includesa range from about 800 MHz to about 2.5 GHz.

In still another embodiment, gain characteristics of the amplifierinclude at least two peaks.

In still another embodiment, a first band which is a frequency rangecorresponding to a range from a first gain at a first peak of the gaincharacteristics of the amplifier to −3 dB of the first gain, includes1.5 GHz and, a second band which is a frequency range corresponding to arange from a second gain at a second peak of the gain characteristics ofthe amplifier to −3 dB of the second gain, includes 1.9 GHz.

In still another embodiment, a first band which is a frequency rangecorresponding to a range from a first gain at a first peak of the gaincharacteristics of the amplifier to −3 dB of the first gain, includes900 MHz and, a second band which is a frequency range corresponding to arange from a second gain at a second peak of the gain characteristics ofthe amplifier to −3 dB of the second gain, includes 1.9 GHz.

In still another embodiment, the first switch and the amplifier areformed on one and the same semiconductor substrate.

In still another embodiment, at least one of the first passive circuitand the second passive circuit is formed on the semiconductor substrate.

In still another embodiment, the first passive circuit receives andoutputs an analog signal and the second passive circuit receives andoutputs a digital signal.

In still another embodiment, the first passive circuit receives andoutputs a first digital signal and the second passive circuit receivesand outputs a second digital signal.

In still another embodiment, the first passive circuit receives andoutputs a signal having a first frequency and the second passive circuitreceives and outputs a signal having a second frequency, the firstfrequency and the second frequency being different from each other.

In still another embodiment, the first frequency is higher than thesecond frequency.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstpassive circuit having an input terminal and an output terminal; asecond passive circuit having an input terminal and an output terminal;a first switch having a single-pole terminal and two multi-throwterminals; a second switch having a single-pole terminal and twomulti-throw terminals; a third switch having a single-pole terminal andtwo multi-throw terminals; a front end circuit; and an antenna. One ofthe multi-throw terminals of the first switch is connected to the inputterminal of the first passive circuit and the other of the multi-throwterminals of the first switch is connected to the input terminal of thesecond passive circuit. One of the multi-throw terminals of the secondswitch is connected to the output terminal of the first passive circuitand the other of the multi-throw terminals of the second switch isconnected to the output terminal of the second passive circuit. One ofthe multi-throw terminals of the third switch is connected to thesingle-pole terminal of the second switch, the other of the multi-throwterminals of the third switch is connected to the front end circuit andthe single-pole terminal of the third switch is connected to theantenna.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstpassive circuit having an input terminal and an output terminal; asecond passive circuit having an input terminal and an output terminal;a first switch having a single-pole terminal and two multi-throwterminals; a first antenna; and a second antenna. One of the multi-throwterminals of the first switch is connected to the input terminal of thefirst passive circuit and the other of the multi-throw terminals of thefirst switch is connected to the input terminal of the second passivecircuit. The output terminal of the first passive circuit is connectedto the first antenna and the output terminal of the second passivecircuit is connected to the second antenna.

In one embodiment, the power amplifier further includes: a third passivecircuit having an input terminal and an output terminal; a fourthpassive circuit having an input terminal and an output terminal; asecond switch having a single-pole terminal and two multi-throwterminals; and a third switch having a single-pole terminal and twomulti-throw terminals. One of the multi-throw terminals of the secondswitch is connected to the input terminal of the third passive circuitand the other of the multi-throw terminals of the second switch isconnected to the input terminal of the fourth passive circuit. One ofthe multi-throw terminals of the third switch is connected to the outputterminal of the third passive circuit and the other of the multi-throwterminals of the third switch is connected to the output terminal of thefourth passive circuit.

In another embodiment, the power amplifier further includes a fourthswitch having a single-pole terminal and two multi-throw terminals. Oneof the multi-throw terminals of the fourth switch is connected to theoutput terminal of the first passive circuit and the other of themulti-throw terminals of the fourth switch is connected to the outputterminal of the second passive circuit.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstpassive circuit having an input terminal and an output terminal; asecond passive circuit having an input terminal and an output terminal;a third passive circuit having an input terminal and an output terminal;a fourth passive circuit having an input terminal and an outputterminal; a first switch having a single-pole terminal and twomulti-throw terminals; a second switch having a single-pole terminal andtwo multi-throw terminals; a third switch having a single-pole terminaland two multi-throw terminals; a fourth switch having a single-poleterminal and two multi-throw terminals; a fifth switch having asingle-pole terminal and two multi-throw terminals; an amplifier havingan input terminal and an output terminal; a front end circuit; and anantenna. One of the multi-throw terminals of the first switch isconnected to the input terminal of the first passive circuit, the otherof the multi-throw terminals of the first switch is connected to theinput terminal of the second passive circuit and the output terminal ofthe amplifier is connected to the single-pole terminal of the firstswitch. One of the multi-throw terminals of the second switch isconnected to the input terminal of the third passive circuit and theother of the multi-throw terminals of the second switch is connected tothe input terminal of the fourth passive circuit. One of the multi-throwterminals of the third switch is connected to the output terminal of thethird passive circuit and the other of the multi-throw terminals of thethird switch is connected to the output terminal of the fourth passivecircuit. One of the multi-throw terminals of the fourth switch isconnected to the output terminal of the first passive circuit and theother of the multi-throw terminals of the fourth switch is connected tothe output terminal of the second passive circuit. One of themulti-throw terminals of the fifth switch is connected to thesingle-pole terminal of the fourth switch, the other of the multi-throwterminals of the fifth switch is connected to the front end circuit andthe single-pole terminal of the fifth switch is connected to theantenna.

According to still another aspect of the present invention, acommunication unit is provided. The communication unit includes: a firstpassive circuit having an input terminal and an output terminal; asecond passive circuit having an input terminal and an output terminal;a third passive circuit having an input terminal and an output terminal;a fourth passive circuit having an input terminal and an outputterminal; a first switch having a single-pole terminal and twomulti-throw terminals; a second switch having a single-pole terminal andtwo multi-throw terminals; a third switch having a single-pole terminaland two multi-throw terminals; an amplifier having an input terminal andan output terminal; a first antenna; and a second antenna. One of themulti-throw terminals of the first switch is connected to the inputterminal of the first passive circuit, the other of the multi-throwterminals of the first switch is connected to the input terminal of thesecond passive circuit and the output terminal of the amplifier isconnected to the single-pole terminal of the first switch. One of themulti-throw terminals of the second switch is connected to the inputterminal of the third passive circuit and the other of the multi-throwterminals of the second switch is connected to the input terminal of thefourth passive circuit. One of the multi-throw terminals of the thirdswitch is connected to the output terminal of the third passive circuitand the other of the multi-throw terminals of the third switch isconnected to the output terminal of the fourth passive circuit. Theoutput terminal of the first passive circuit is connected to the firstantenna and the output terminal of the second passive circuit isconnected to the second antenna.

Thus, the invention described herein makes possible the advantages ofproviding a power amplifier which is commonly applicable to differentsystems (i.e., the systems having different frequency bands, outputpowers to be transmitted and modulation types) and can be formed in areduced size at lower costs, and providing a highly value-addedcommunication unit by using such a power amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention may be better understood and its numerous objects andadvantages will become apparent to those skilled in the art by referenceto the accompanying drawings as follows:

FIG. 1 is a configuration diagram illustrating the first example of theswitchable power amplifier according to the present invention.

FIG. 2 is a diagram illustrating the impedances of matching circuits.

FIG. 3 is a diagram showing the equivalent circuits of an input matchingcircuit PC1 or PC2 and a first GaAs MESFET PA101.

FIG. 4 is a diagram showing a specific implementation of the switchablepower amplifier in this example.

FIG. 5 is a diagram showing an exemplary configuration of a switchablepower amplifier having a feedback control section.

FIG. 6 is a diagram showing another exemplary configuration of aswitchable power amplifier having a feedback control section.

FIG. 7 is a block diagram of a generally used information communicationunit.

FIG. 8 is a configuration diagram of an information communication unitusing the switchable power amplifier according to the present invention.

FIG. 9 is a configuration diagram of a first DPDT switch 152 in whichthe first single-pole-dual-throw switch 139 and the secondsingle-pole-dual-throw switch 140 in FIG. 8 have been combined.

FIG. 10 is a configuration diagram of a transmission/reception selectingswitch for a diversity transmission/reception using the two antennas andthe two filters for Mode 2 shown in FIG. 8.

FIG. 11 is a configuration diagram of a communication unit using theswitchable power amplifiers according to the present invention.

FIG. 12 is a diagram showing parts to be implemented as MMICs in thepower amplifier of the present invention.

FIG. 13 is a configuration diagram in which the switchable poweramplifier 109 of this example is implemented by MMICs and hybrid ICs.

FIG. 14 is a configuration diagram of the second example of theswitchable power amplifier according to the present invention.

FIG. 15 is a circuit diagram of switches SW1 and SW2.

FIG. 16 is a circuit diagram of switches SW3 and SW4.

FIG. 17 is a configuration diagram of the switchable power amplifier inthe second example.

FIG. 18 is a diagram showing ranges implemented as MMICs in thisexample.

FIG. 19 is a graph illustrating a 3 dB band width.

FIG. 20 is a graph illustrating a 3 dB band width of an amplifier havingtwo peaks.

FIG. 21 is a configuration diagram of the third example of theswitchable power amplifier according to the present invention.

FIG. 22 is a diagram illustrating the wide-band operation of a poweramplifier.

FIG. 23 is a configuration diagram of the switchable power amplifier inthe third example.

FIG. 24 is a diagram showing parts implemented as MMICs in the thirdexample.

FIG. 25 is a configuration diagram of the fourth example of theswitchable power amplifier according to the present invention.

FIG. 26 is a configuration diagram of the switchable power amplifier inthe fourth example.

FIG. 27 is a diagram showing parts implemented as MMICs in the fourthexample.

FIG. 28 is a configuration diagram of the fifth example of theswitchable power amplifier according to the present invention.

FIG. 29 is a configuration diagram of the switchable power amplifier inthe fifth example.

FIG. 30 is a diagram showing parts implemented as MMICs in the fifthexample.

FIG. 31 is a configuration diagram of the sixth examples of theswitchable power amplifier according to the present invention.

FIG. 32 is a configuration diagram of the switchable power amplifier inthe sixth example.

FIG. 33 is a diagram showing a part implemented as an MMIC in the sixthexample.

FIG. 34 is a configuration diagram in which a secondsingle-pole-dual-throw switch SW2 is connected to the respective outputterminals of a first passive circuit PC1 and a second passive circuitPC2 connected to the dual-throw terminals of a firstsingle-pole-dual-throw switch SW1 in the power amplifier shown in FIG.31.

FIG. 35 is a block diagram of a conventional example.

FIG. 36 is a simplified circuit diagram of a radio frequency (RF)integrated circuit described in Japanese Laid-Open Patent PublicationNo. 8-88524.

FIG. 37 shows a graph showing the variations in distortion and poweradded efficiency with respect to an input power and a graph showing thevariation in output power with respect to the input power in the circuitshown in FIG. 36.

FIG. 38 is a graph showing the input power dependences of the outputmatching circuits PC1 and PC2.

FIG. 39 is a block diagram of a power amplifier and a communication unitaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the examples of the present invention will be describedwith reference to the accompanying drawings, in which the same referencenumerals denote the same components.

In this specification, a “switch” without any modifier means a“single-pole-multi-throw switch” unless specifically stated otherwise. Aswitch in the present specification includes a single-pole terminal andtwo multi-throw terminals. On the other hand, a “power amplifier” and a“communication unit” in this specification respectively include aswitchable power amplifier and a switching information communicationunit, as will be described later.

EXAMPLE 1

The switchable power amplifier according to the present invention has afunction of transmitting RF signals having two different frequencies andtwo different output powers by temporally synchronizing the switching oftwo switches.

The switchable power amplifier of this example can output the RF signalsfor Modes 1 and 2 shown in the following table. In Mode 1, thetransmission frequency f=f1 and the output power Pout=Pout1. On theother hand, in Mode 2, the transmission frequency f=f2 and the outputpower Pout=Pout2. The communication types and the modulation types inModes 1 and 2 are as shown in the following table.

Communica- f Pout tion type Mode 1 f1 1.9 GHz Pout1 22 dBm DigitalModulation Mode 2 f2 2.4 GHz Pout2 26 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: spread spectrum (SS) QPSK modulationtype

FIG. 1 is a configuration diagram showing the first example of theswitchable power amplifier according to the present invention.

A first single-pole-dual-throw switch SW1, a first input matchingcircuit PC1 for Mode 1 and a second input matching circuit PC2 for Mode2 are connected to the input side of a first power amplifier PA1. On theother hand, a second single-pole-dual-throw switch SW2, a second poweramplifier PA2 for Mode 1 and a third power amplifier PA3 for Mode 2 areconnected to the output side of the first power amplifier PA1.

In Mode 1, the switch SW1 connects the output terminal of the inputmatching circuit PC1 to the input terminal of the power amplifier PA1and the switch SW2 connects the output terminal of the power amplifierPA1 to the input terminal of the power amplifier PA2. On the other hand,in Mode 2, the switch SW1 connects the output terminal of the inputmatching circuit PC2 to the input terminal of the power amplifier PA1and the switch SW2 connects the output terminal of the power amplifierPA1 to the input terminal of the power amplifier PA3. As a result, an RFsignal in Mode 1 is received at an input terminal Pin1 and outputthrough an output terminal Pout1. On the other hand, an RF signal inMode 2 is received at an input terminal Pin2 and output through anoutput terminal Pout2.

The first power amplifier PA1 includes a first GaAs MESFET (GaAsmetal-semiconductor FET) PA101. The second power amplifier PA2 includes:a second GaAs MESFET PA201; a first inter-stage matching circuit PA202;and a first output matching circuit PA203. The third power amplifier PA3includes: a third GaAs MESFET PA301; a second inter-stage matchingcircuit PA302; and a second output matching circuit PA303.

The first, second and third GaAs MESFETs PA101, PA201 and PA301 includedin the first, second and third power amplifiers PA1, PA2 and PA3 are ofa depletion type and have gate widths (Wg) of 1 mm, 4 mm and 8 mm,respectively.

The first and the second GaAs MESFETs PA101 and PA201 having Wg of 1 mmand 4 mm, respectively, are mounted in resin-molded packages, while thethird GaAs MESFET PA301 having Wg of 8 mm is mounted in a ceramicpackage (i.e., mounted on a ceramic carrier and then sealed with aresin).

Each of the first and the second single-pole-dual-throw switches SW1 andSW2 may be implemented as a circuit using a PIN diode (i.e., a circuitincluding a resin-molded PIN diode and peripheral circuits of the PINdiode such as a capacitor for cutting DC and a choke coil having aresistance component and an inductance component) or as an integratedcircuit using a GaAs MESFET (i.e., a circuit formed by integrating aGaAs MESFET with peripheral components thereof and molding them with aresin).

The operating power supply voltages of the first, second and third GaAsMESFETs PA101, PA201 and PA301 are as follows. Specifically, the drainvoltages thereof are about 3.5 V and the gate voltages thereof arenegative voltages in the range from about −2.0 V to about −3.0 V. Thefirst GaAs MESFET PA101 is operated while paying much respect to thegain thereof and the second and the third GaAs MESFETs PA201 and PA301are operated in a class AB (with an idle current corresponding to about10% of Idss) while paying much respect to the linearity of theinput/output characteristics and the digital distortion characteristicsthereof. “Idss” herein refers to a drain-source current in the statewhere the gate and the source are short-circuited (i.e., at the time ofzero bias). The first, second and third GaAs MESFETs have Idss of about250 mA, 900 mA and 1.7 A, respectively.

In this example, the control voltages for the first and the secondsingle-pole-dual-throw switches SW1 and SW2 are set at the two levels of0 V/12 V in the case of a circuit using a PIN diode or at the two levelsof 0 V/−4.7 V in the case of an integrated circuit using a GaAs MESFET.

The input matching circuits, the inter-stage matching circuits and theoutput matching circuits included in the first, second and third poweramplifier PA1, PA2 and PA3 have such functions and configurations as tosatisfy the desired characteristics in accordance with frequencies,output powers and modulation types.

FIG. 2 is a diagram illustrating the impedances of matching circuits.The input impedances of a GaAs MESFET are different from each other atfrequencies f1 and f2 . Thus, the first and the second input matchingcircuits PC1 and PC2 equalize the impedance of a signal source Zs (inthis case, a transmission RF section such as a transmission mixersection connected to an external circuit is assumed to be an impedanceviewed from the switchable power amplifier) with the input impedance ZI1of the first GaAs MESFET PA101 (i.e., performs an impedance matchingtherebetween) at the frequency f1 (1.9 GHz) and at the frequency f2 (2.4GHz), respectively. As a result, an input return loss is optimized. Thereturn loss is preferably 6 dB or more.

The first inter-stage matching circuit PA202 performs a matching suchthat the output impedance Z01 of the first GaAs MESFET PA101 is equal tothe input impedance ZI2 of the second GaAs MESFET PA201 at the frequencyf1 . The first output matching circuit PA203 performs a matching suchthat the output impedance ZO2 of the second GaAs MESFET PA201 is equalto a load impedance ZU on an antenna side at the frequency f1.

The second inter-stage matching circuit PA302 and the second outputmatching circuit PA303 also perform similar matchings at the frequencyf2 . The first inter-stage stage matching circuit PA202 and the firstoutput matching circuit PA203 are loads of the first and the second GaAsMESFETs PA101 and PA201, respectively, at the frequency f1 . On theother hand, the second inter-stage matching circuit PA302 and the secondoutput matching circuit PA303 are loads of the first and the third GaAsMESFETs PA101 and PA301, respectively, at the frequency f2 . These loadsare important parameters determining the output characteristics (i.e.,the output powers, the saturation output powers, the 1 dB compressionpoint output powers, the linear gains, the power added efficiencies, theoperational currents and the distortions (specifically, intermodulationdistortions and adjacent channel leakage powers)) of the first, secondand third GaAs MESFETs PA101, PA201 and PA301.

In the π/4 shift DQPSK modulation type and the spread spectrum (SS) QPSKmodulation type in this example, it is important that the distortioncharacteristics are satisfactory. Thus, a linear amplifier is requiredto be used as a power amplifier. From this point of view, in Mode 1 (1.9GHz, 22 dBm, n/4 shift DQPSK modulated signal), the inter-stage matchingcircuit PA202 performs a matching such that the GaAs MESFET PA101 cansecure an output power (i.e., a gain) high enough to drive the GaAsMESFET PA201. When the output power Pout1 is equal to 22 dBm, the outputmatching circuit PA203 suppresses a ratio of an adjacent channel leakagepower to a carrier output (i.e., the ratio of a leak power at anadjacent channel frequency with respect to an output power at a carrierfrequency) to a minimal level and then performs a matching so as toattain a high power added efficiency (i.e., the ratio of an input DCpower to a consumed RF power).

In Mode 2 (2.4 GHz, 26 dBm, spread spectrum (SS) QPSK modulated signal),the inter-stage matching circuit PA302 performs a matching such that theGaAs MESFET PA101 can secure an output power (i.e., a gain) high enoughto drive the GaAs MESFET PA301. When the output power Pout2 is equal to26 dBm, the output matching circuit PA303 suppresses an adjacent channelleakage power and an intermodulation distortion (IMD: frequencycomponents represented by “mfa±nfb” [where n and m are integers] causedwhen a plurality of different signals are amplified) to minimal levelsand then performs a matching so as to attain a high power addedefficiency.

In this way, the inter-stage matching circuits and the output matchingcircuits of the power amplifier according to the present invention canbe configured so as to satisfy the desired characteristics in accordancewith the frequencies, the output powers and the modulation types of RFsignals.

FIG. 3 is a diagram showing the equivalent circuits of one of the inputmatching circuits PC1 or PC2 and the first GaAs MESFET PA101. The firstGaAs MESFET PA101 includes a drain 101, a source 102 and a gate 103. Thedrain 101 is connected to a power supply terminal 1011 via a chokeinductor 104. The source 102 is connected to a ground via a sourceinductor 105. An RF signal is input to a terminal 1031 and outputthrough a terminal 1012. The input matching circuit PC1 can berepresented by a serial inductance 106, a serial capacitance 107 and aparallel capacitance 108 which are lumped constant element components.It is noted that the equivalent circuits of each of an inter-stagematching circuit and an output matching circuit can also be representedby lumped constant element components in a similar manner. Thus, aninput matching circuit, an inter-stage matching circuit or an outputmatching circuit can be configured as a combination of lumped constantelements other than that of the circuit shown in FIG. 3. For example, inthis example, the lumped constant elements forming the matching circuitare implemented by using various chip components such as a chipinductor, a chip capacitor and a chip resistor.

FIG. 4 is a diagram showing a specific implementation of the switchablepower amplifier in this example. The components of the switchable poweramplifier 109, as well as drain voltage/gate voltage supply sections110, 111 and 112 (respectively for the first, second and third GaAsMESFETs PA101, PA201 and PA301), and control voltage supply sections 113and 114 (respectively for the first and the secondsingle-pole-dual-throw switches SW1 and SW2), are mounted on a printedcircuit board 115. Vdd1/Vgg1, Vdd2/Vgg2 and Vdd3/Vgg3 denote the drainvoltages/gate voltages to be supplied to the first, second and thirdGaAs MESFETs PA101, PA201 and PA301, respectively. VC1 and VC2 denotethe control voltages to be supplied to the first and the secondsingle-pole-dual-throw switches SW1 and SW2, respectively.

The drain voltage/gate voltage supply section 110 controls at least oneof the drain voltage and the gate voltage for the first GaAs MESFETPA101, thereby reducing the power consumption of PA101 when theoperation of PA101 is unnecessary. In the same way, the drainvoltage/gate voltage supply sections 111 and 112 control at least one ofthe drain voltage and the gate voltage for the second and the third GaAsMESFETs PA201 and PA301, respectively, thereby reducing the powerconsumption thereof.

As a method for reducing the power consumption of a GaAs MESFET, amethod for reducing the drain current Id of the FET by controlling thedrain voltage or the gate voltage can be used. For example, in the caseof a GaAs MESFET of a depletion type, the drain current Id can bereduced by lowering the drain voltage from about 3.5 V during the normaloperation to about 0.0 V during the non-operation. Alternatively, thedrain current Id may be reduced by lowering the gate voltage from about−2.5 V during normal operation to about −5.0 V during non-operation. Thedrain voltage/gate voltage supply section 110 receives at least one ofthe drain voltage Vdd1 (e.g., 3.5 V) for normal operation and the gatevoltage Vgg1 (e.g., −2.5 V) for normal operation from an external powersupply, varies Vdd1 or Vgg1 depending upon whether the first GaAs MESFETPA101 is activated or deactivated and then outputs varied Vdd1 or Vgg1to PA101. The drain voltage/gate voltage supply sections 111 and 112function similarly to the drain voltage/gate voltage supply section 110.

The power supply controls of the drain voltage/gate voltage supplysections 110, 111 and 112 are performed in association with those of thecontrol voltage supply sections 113 and 114 for the first and the secondsingle-pole-dual-throw switches SW1 and SW2. More specifically, in Mode1, i.e., in a mode in which RF signals are received through the inputterminal Pin1 and output through the output terminal Pout1, the controlvoltage supply sections 113 and 114 receive the control voltages VC1 andVC2, respectively, thereby controlling SW1 and SW2 such that SW1 and SW2select Pin1 and Pout1, respectively. In addition, in this Mode 1, sincePA301 is not required to be operated, the drain current Id is reduced,thereby realizing a low power consumption.

The drain voltage/gate voltage supply section is implemented by a chipinductor as a choke and a bypass capacitor or by a microstrip line formounting a switchable power amplifier on a printed circuit board and abypass capacitor.

It is noted that, when the output powers defined in Modes 1 and 2 aredifferent as in this example or when the transmission/receptionconditions of the RF signals are variable, it is necessary to vary orstabilize the output powers. Thus, since a gain control function forstabilizing an output power and holding a constant power isindispensable as a function of a transmission power amplifier, anattenuator or a power amplifier having an auto gain control (AGC) or anauto level control (ALC) is integrated into the power amplifier, therebyfeedbacking and controlling the monitored output power. The output powercan be monitored by a capacitance coupling or a directional coupler.

FIG. 5 is a diagram showing an exemplary implementation of a switchablepower amplifier having a feedback control section. As shown in FIG. 5, afirst attenuator 117 is provided on the input side of the first poweramplifier PA1 of this example and/or a second attenuator 118 is providedon the external input side of the switchable power amplifier 109 of thisexample. These attenuators are controlled by a feedback control section116 for monitoring the output power and supplying a control signal.

As an attenuator, a fixed type attenuator (π-type, T-type attenuator)using a chip resistor or an electronic attenuator such as an IC using ananalog type PIN diode, GaAs MESFET or the like and an IC formed byserially connecting digital type unit attenuators (ICs using GaAsMESFETs or the like) to be electronically controlled individually can beused. A “unit attenuator” is an element using an impedance between thedrain and the source of a single GaAs MESFET for attenuating a signal.When the gate voltage of a unit attenuator is controlled, theattenuation amount is also varied. Since a unit attenuator has anattenuation amount of about 0.5 dB to about 5.0 dB, for example, if afurther attenuation is desired, a plurality of unit attenuators arerequired to be serially connected.

FIG. 6 is a diagram showing another exemplary implementation of aswitchable power amplifier having a feedback control section. As shownin FIG. 6, by varying the power supply voltage (e.g., lowering the drainvoltage or reducing the gate voltage) of the auto gain control poweramplifier 119 provided on the external input side of the first poweramplifier PA1 of this example or the switchable power amplifier 109 ofthis example in accordance with the monitored output power, the gain andthe output power are adjusted.

FIG. 7 is a block diagram of a generally used information communicationunit. The sections related to the transmission/reception and the signalprocessing of an RF signal are divided into a radio frequency (RF)section 120, an intermediate frequency (IF) signal processing section121 and a base band section 122.

The RF section 120 includes: an antenna 123 used for transmission andreception; an antenna duplexer or a switch 124; and a front-end section125. The front-end section 125 further includes a transmission section126 and a reception section 127. Though, in general, a “front-endsection” sometimes refers to a reception section only, a “front-endsection” is herein assumed to include a transmission section.

The transmission section 126 is mainly composed of: a transmission mixer(up-converter) for converting an intermediate frequency (IF) signalsupplied from a modulator to an RF signal; a voltage control oscillator(VCO) thereof; and a power amplifier for amplifying the RF signal(herein including an RF amplifier for a small signal). The switchablepower amplifier 109 of this example belongs to this section.

The reception section 127 is mainly composed of a low noise amplifier(LNA) for amplifying the RF signal transmitted from the antenna 123 anda reception mixer. (down-converter) for converting an RF signal into alow-frequency IF signal such that the signal can be processed by an IC.

The IF signal processing section 121 is mainly composed of a section (amixer and an IF amplifier) for further converting and amplifying an IFsignal supplied from a modulation section of a base band signal to besupplied to the transmission section and from the front-end section ofthe reception section.

In a digital system, the base band section is mainly composed of: aCODEC for performing encoding and decoding processing on an audio, dataor video signal; a CODEC for performing a channel selection and the likein accordance with the transmission multiplexing type (time division,frequency division or code division); a base band signal (audio, data orvideo signal) modulation section (for modulating the base band signalinto an IF signal for the transmission side); and an IF signaldemodulation section (for demodulating the IF signal into a base bandsignal for the reception side). In an analog system, the base bandsection 122 is mainly composed of: a demodulation section (frequencydiscriminator); a modulation section; and an audio/data signalprocessing section. Depending upon the communication type, the base bandsection processes either an analog signal or a digital signal. Thus, anIC dedicated for processing an analog signal and an IC dedicated forprocessing a digital signal are separately used for these two types.Alternatively, an integrated IC commonly used for processing both ananalog signal and a digital signal may be used.

Additionally, a CPU/memory section 128 and a power supply section 129are also provided for controlling the respective sections. TheCPU/memory section 128 controls the RF section 120, the IF signalprocessing section 121 and the base band section 122 in accordance withthe desired communication type. The power supply section 129 generates apositive power or a negative power from a battery or a commercial powersupply in accordance with the operating voltages of the respectivecircuits by using a DC/DC converter, a regulator or the like.

By integrating the RF section 120, the IF signal processing section 121and the base band section 122 on at least one printed circuit board(e.g., a dielectric substrate or the like) and collectively mountingthem into the case of an information communication unit, the unit can bedownsized at lower cost as compared with a conventional example. As aresult, a highly value-added information communication terminal unitcommonly applicable to systems having different frequency bands,transmission output powers and modulation types can be obtained.

FIG. 8 is a configuration diagram using the switchable power amplifieraccording to the present invention. The information communication unitshown in FIG. 8 includes switches for switching transmission andreception corresponding to Modes 1 and 2, respectively. A secondsingle-pole-dual-throw switch 140 and a third single-pole-dual-throwswitch 141 corresponding to Modes 1 and 2, respectively, are connectedto the output side of the switchable power amplifier 138 of the presentinvention. The switches 140 and 141 play a role of switchingtransmission and reception (Mode 1: switching between TX1 and RX1 andMode 2: switching between TX2 and RX2).

A first antenna 142 (for Mode 1) and a first filter 144 are connected tothe single-pole side of the second single-pole-dual-throw switch 140,while a second antenna 143 (for Mode 2) and a second filter 1451 areconnected to the single-pole side of the third single-pole-dual-throwswitch 141. A first low-noise amplifier 146, a first local amplifier 147and a first mixer 148 are connected to the side of a reception terminalRX1 for Mode 1, while a second low-noise amplifier 149, a second localamplifier 150 and a second mixer 151 are connected to the side of areception terminal RX2 for Mode 2.

FIGS. 9(a) and 9(b) are diagrams showing a specific exemplaryimplementation of a first DPDT (dual-pole-dual-throw) switch 152 inwhich the two single-pole-dual-throw switches shown in FIG. 8, i.e., thefirst single-pole-dual-throw switch 139 and the secondsingle-pole-dual-throw switch 140, have been combined. The single-poleterminal P1 of the first single-pole-dual-throw switch 139, thesingle-pole terminal P2 of the second single-pole-dual-throw switch 140,a throw terminal T1 (on the side of transmission for Mode 2) of thefirst single-pole-dual-throw switch 139 and a throw terminal T2 (on theside of reception for Mode 1) of the second single-pole-dual-throwswitch 140 correspond to the respective ports of the first DPDT switch152. The first, second, third and fourth switching transistors TSW1,TSW2, TSW3 and TSW4 are connected between adjacent ports P1 & P2, P2 &T2, T2 & T1 and T1 & P1, respectively. The fifth, sixth, seventh andeighth switching transistors TSW5, TSW6, TSW7 and TSW8 are connected inparallel to the port terminals P1, P2, T2 and T1, respectively. It isnoted that TSW5 to TSW8 are sometimes connected and sometimesdisconnected depending upon the desired isolation between adjacentports. Thus, the adjacent ports are connected to each other via an SPST(single-pole-single-throw) switch. As a result, the first DPDT switch152 can play a role of switching a signal received at P1 to P2 or to T1and switching a signal received at P2 to T2.

FIGS. 10(a) and 10(b) are diagrams showing a specific exemplaryimplementation of a transmission/reception selecting switch forperforming a diversity transmission/reception by using two antennas forMode 2 (a second antenna 143 and a third antenna 154) and two filters (asecond filter 1451 and a third filter 1452) in place of those shown inFIG. 8. In this diversity system, an antenna having satisfactorytransmission/reception characteristics is selected depending upon thevariable transmission/reception conditions affected by the reflectionand the scattering of radio waves. A transmission/reception selectingswitch is implemented by a second DPDT switch 153. P1′ (on the side ofthe second antenna; for Mode 2), P2′ (on the side of the third antenna;for Mode 2), T1′ (on the side of transmission for Mode 2) and T2′ (onthe side of reception for Mode 2) correspond to the respective ports ofthe second DPDT switch 153. The ninth, tenth, eleventh and twelfthswitching transistors TSW9, TSW10, TSW11 and TSW12 are connected betweenadjacent ports P2′ & T1′, T1′ & P1′, P1′ & T2′ and T2′ & P2′,respectively. The thirteenth, fourteenth, fifteenth and sixteenthswitching transistors TSW13, TSW14, TSW15 and TSW16 are connected inparallel to the port terminals P2′, T1′, P1′ and T2′, respectively. Itis noted that TSW13 to TSW16 are sometimes connected and sometimesdisconnected depending upon the desired isolation between adjacentports. Thus, the adjacent ports are connected to each other via an SPST(single-pole-single-throw) switch. As a result, by selecting either oneof the ports P1′ and P2′ on the antenna side, the port T2′ on thetransmission side and T2′ on the reception side can be switched.

FIG. 11 is a configuration diagram of a communication unit using theswitchable power amplifiers of the present invention. Unlike in FIG. 8,a single antenna section is commonly used in both Modes 1 and 2. Aswitch 155 for switching the outputs for Modes 1 and 2 and a switch 156for switching transmission and reception of the switchable poweramplifier are used.

A first single-pole-dual-throw switch 155 for switching Modes 1 and 2 isconnected to the output side of the switchable power amplifier 138 ofthe present invention and a second single-pole-dual-throw switch 156playing a role of switching transmission and reception (Mode 1:switching between TX1 and RX1 and Mode 2: switching between TX2 and RX2)is subsequently connected thereto. A filter 157 (commonly used for Modes1 and 2) and an antenna 158 (commonly used for Modes 1 and 2) areconnected to the side of the single pole of the secondsingle-pole-dual-throw switch 156.

It is noted that a GaAs MESFET, a single-pole-dual-throw switch, aninput matching circuit, an inter-stage matching circuit or an outputmatching circuit may be implemented by a configuration using a hybrid ICor an MMIC by methods other than that described above. Hereinafter theconfiguration and mounting methods of (1) a hybrid IC and (2) an MMICwill be described so as to include the above-described method.

It is noted that, in this specification, “discrete components” mean thecomponents of the hybrid IC as will be described in the following item(1). More specifically, the discrete components include various chipcomponents such as a chip capacitor, a chip inductor, a chip resistorand a chip FET and components packaged within an MMIC. This definitionis also applicable to the examples to be described later.

(1) Hybrid IC (HIC)

The above-described components are individually mounted on a printedcircuit board. A “printed circuit board” herein means a substrate onwhich an RF section, an IF signal processing section or a base bandsection is mounted (hereinafter, such a substrate will also be referredto as a “mother substrate”). Hereinafter, the exemplary implementationsof a hybrid IC will be separately described with respect to (1.1) a GaAsMESFET, (1.2) a single-pole-dual-throw switch, (1.3) a passive circuitand (1.4) the combination of (1.1) to (1.3).

(1.1) GaAs MESFET

(a) Mount a GaAs MESFET in a resin-molded package or a ceramic package(mounted on a ceramic carrier and then sealed with a resin).

(b) Use a bare chip and mount a GaAs MESFET onto a printed circuit boardin a “back-to-face” manner by using silver paste or the like (i.e., suchthat a surface of the chip on which active elements and the like are notformed faces the principal surface of the printed circuit board) or in a“face-to-face” manner (i.e., such that the principal surface of the chipon which micro bumps and the like are formed on the active elements andthe pads faces the principal surface of the printed circuit board).

(1.2) Single-pole-dual-throw Switch

(a) Use a circuit including a PIN diode (a resin-molded PIN diode andperipheral circuits thereof).

(b) Use an integrated circuit including a GaAs MESFET (i.e., a circuitin which the GaAs MESFET and the peripheral circuits thereof areintegrated and molded with a resin).

(1.3) Passive Circuit (A Passive Circuit Including an Input MatchingCircuit, an Inter-stage Matching Circuit and an Output Matching Circuit)

(a) Use chip components (such as a chip inductor, a chip capacitor and achip resistor).

(b) Use a semiconductor substrate (forming an MMIC in the strict sense).

In general, various lumped constant elements are formed on asemiconductor substrate (made of a compound semiconductor such as Si,GaAs or the like). Among the lumped constant elements, the inductancecomponents are implemented by forming microstrip lines (such ashigh-impedance lines), spiral inductors or the like. The capacitancecomponents are implemented by forming MIM (metal-insulator-metal)capacitors, comb capacitors or the like. The resistance components areimplemented by forming thin-film resistances (such as NiCr), ionimplanted resistances, resistances using active elements or the like.

As the distributed constant elements, end-open stubs, end-short stubs orthe like are formed by patterning for implementing the inductancecomponents, the capacitance components and the like.

These elements may be mounted in a bare chip manner. Alternatively,these elements may be mounted on a printed circuit board by sealingmultiple chips including a GaAs MESFET chip within a single package.

(c) Use a dielectric substrate, in which case strip lines, MIMcapacitors and thin-film resistances are formed on a printed circuitboard (made of glass epoxy: εr=4.9; glass fluoride or teflon: εr=2.6;glass thermosetting PPO resin: εr=3.5, 10.5; etc.), a ceramic substrate(made of alumina, etc.) or the like.

Among these printed circuit boards, the substrate made of glass epoxy isused as a mother substrate on which the RF section, the IF signalprocessing section and the base band section are mounted. The substratemade of glass thermosetting PPO resin may also be implemented as amulti-layer substrate including strip lines, thin-film resistances andthe like formed between adjacent layers. The ceramic substrate may alsobe mounted so as to be one of the multiple chips including othercomponents by forming the substrate as a pattern in the carrier sectionof a ceramic package.

(1.4) Combination of (1.1) to (1.3)

For example, as a passive circuit including matching circuits, a part tobe fabricated on a semiconductor substrate, a part using chip componentsand a part to be formed by pattering on a printed circuit board areseparately configured. The passive circuit fabricated on thesemiconductor substrate may be one (such as a GaAs chip) of the multiplechips including other components or integrated as an MMIC to bedescribed below.

(2) MMIC

The above-described individual components are implemented as MMICs(monolithic microwave ICs). Hereinafter, the MMIC implementations willbe described so as to correspond to the configurations employed in thisexample. FIG. 12 is a diagram showing parts to be implemented as MMICsin the power amplifier of the present invention. The followingdescription corresponds to the numbered alphabets (A) and (B)-1 to (B)-9used in FIG. 12. In FIG. 12, a portion surrounded by broken lines is apart to be implemented as an MMIC.

(A) All of the switchable power amplifier of this example is implementedas an MMIC. That is to say, all the components of the switchable poweramplifier of this example including the first, second and third poweramplifiers PA1, PA2 and PA3, the first and the secondsingle-pole-dual-throw switches SW1 and SW2, the first and the secondinput matching circuits PC1 and PC2, the first and the secondinter-stage matching circuits PA202 and PA302 and the first and thesecond output matching circuits PA203 and PA303 are implemented as anMMIC.

(B) An arbitrary part of the switchable power amplifier of this exampleis selectively implemented as an MMIC. More specifically, components tobe implemented as an MMIC are selected from the secondsingle-pole-multi-throw switch SW2, the power amplifier PA1 connected tothe single-pole terminal of the second single-pole-multi-throw switchSW2 and the second and the third power amplifiers PA2 and PA3 connectedto the multi-throw terminals of the second single-pole-multi-throwswitch SW2 and then combined on the same semiconductor substrate. Maincombinations thereof are as follows. However, the combinations are notlimited thereto.

(B)-1: Combine the second single-pole-multi-throw switch SW2 with thefirst power amplifier PA1.

(B)-2: Combine the components of (B)-1 with at least one of the othercomponents (the second and the third power amplifiers PA2 and PA3, thefirst and the second input matching circuits PC1 and PC2, etc.).

(B)-3: Combine the second single-pole-multi-throw switch SW2 with atleast one of the components other than the first power amplifier PA1(the second and the third power amplifiers PA2 and PA3, the first andthe second input matching circuits PC1 and PC2, etc.).

(B)-4: Combine the first single-pole-multi-throw switch SW1 with thefirst power amplifier PA1.

(B)-5: Combine the components of (B)-4 with at least one of the othercomponents (the second and the third power amplifiers PA2 and PA3, thefirst and the second input matching circuits PC1 and PC2, etc.).

(B)-6: Combine the first single-pole-multi-throw switch SW1 with atleast one of the components other than the first power amplifier PA1(the second and the third power amplifiers PA2 and PA3, the first andthe second input matching circuits PC1 and PC2, etc.) except for theportion overlapping with (B)-3.

(B)-7: Combine the first single-pole-multi-throw switch SW1, the secondsingle-pole-multi-throw switch SW2 and the first power amplifier PA1.

(B)-8: Combine the components of (B)-7 with at least one of the othercomponents (the second and the third power amplifiers PA2 and PA3, thefirst and the second input matching circuits PC1 and PC2, etc.).

(B)-9: Combine the first power amplifier PA1 with at least one of thecomponents other than the first and the second single-pole-multi-throwswitches SW1 and SW2 (the second and the third power amplifiers PA2 andPA3, the first and the second input matching circuits PC1 and PC2,etc.).

It is noted that an MMIC implementation includes implementing the secondor the third power amplifier PA2 or PA3 as an MMIC and selectivelyimplementing the components of each power amplifier (active elements,passive circuits and the like) as an MMIC (e.g., implementing all thecomponents of the second or the third power amplifier PA2 or PA3 otherthan the output matching circuit thereof as an MMIC). The chipimplemented as an MMIC by any of the combinations (B)-1 to (B)-9 issealed within a resin-molded package or mounted in a bare chip manner.

In this case, the components which are not implemented as an integralpart of the MMIC by any of (A) and (B) are individually mounted on aprinted circuit board as described in the item (1). In order to reducethe costs and improve the performance during practical use, MMICs andhybrid ICs are simultaneously used. In other words, the merits and thedemerits of an MMIC and a hybrid IC are in an inverse relationship to bemutually complemented. On the one hand, an MMIC implementation has amerit of obtaining a high added value by further improving theperformance and reducing the size and the costs to be realized by theintegration of the respective functional components. On the other hand,an MMIC implementation has several demerits including: the increase incosts because of the decrease in production yield during the anteriorprocess (wafer process) and posterior process (assembly process) steps;the deterioration of performance because the components cannot beadjusted individually; and the degradation of characteristics (such as adecrease in gain) or reliability (the thermorunaway or the breakdown ofthe elements) caused by the limit of the heat dissipation of asemiconductor substrate when the output power to be processed becomes 1W or higher. The merits and the demerits of a hybrid IC are inverse tothose of an MMIC.

FIG. 13 is a diagram showing a configuration in which the switchablepower amplifier 109 of this example is implemented by MMICs and hybridICs. This switchable power amplifier 109 includes: a switch-integratedpower amplifier 131 having the above-described implementation (B)-1(i.e., an implementation including the second single-pole-multi-throwswitch SW2 and the first power amplifier PA1 formed on the samesemiconductor substrate); the second and the third power amplifiers 134and 135 implemented as MMICs; the first single-pole-multi-throw switchSW1; and the first and the second input matching circuits 136 and 137implemented as hybrid ICs. The power voltage and the control voltage areconformable to those described with reference to FIG. 4.

It is noted that not only the GaAs MESFETs used as the active elementsfor the above-described power amplifier but also other active elementssuch as enhanced GaAs MESFETs and transistors (e.g., MOSFETs, HBTs,HEMTs, etc.) formed on another semiconductor substrate may be used.

Moreover, a portable unit is currently supposed to satisfy theoperational requirements about an operating voltage of 3.0 V to 3.4 Vcorresponding to that of three NiCd cells or a single Li ion cell.Though the operating power supply voltage of the GaAs MESFET of thisexample is 3.5 V, the operating voltage of any other logic IC may beused. Alternatively, depending upon the type of an informationcommunication unit in question, the power supply voltage of the GaAsMESFET of this example may be set at other values. If optimum activeelements operating within the defined voltage range are used, thepresent example may be implemented at an operating voltage other than3.5 V.

Furthermore, in this example, a negative voltage generated by a DC-DCconverter is used as the gate voltage of the GaAs MESFET. The presentexample may also be implemented by selecting active elements operatingby a single positive power supply so as to eliminate a negative powersupply.

The first, second and third power amplifiers PA1, PA2 and PA3 in thisexample are single-stage amplifiers. Alternatively, multi-stageamplifiers may also be used instead. For example, a driver poweramplifier may be additionally provided on the input side of the firstpower amplifier.

In this example, matching circuits used as passive circuit components ofa power amplifier have been particularly described. Applicable matchingcircuits are not limited to passive components having a matchingfunction, but include various kinds of passive circuits such as a chokeinductor on a power supply line, a bypass capacitor, divided resistancesfor applying a bias, a filter, a harmonic trap circuit and anattenuator. For example, a choke inductor on a power supply line, abypass capacitor and divided resistances for applying a bias may beincluded within a power amplifier implemented as an MMIC. As for afilter, if the transmission frequency and the reception frequency of anRF signal are different from each other, a band-pass filter having apredetermined pass band width may be inserted subsequent to an outputmatching circuit or a harmonic trap circuit may be inserted into theoutput matching circuit.

In this example, RF signals corresponding to two types are transmittedby using single-pole-dual-throw switches. However, a desired poweramplifier and a desired information communication unit may be formedeven by the use of single-pole-multi-throw switches having multiple(three or more) throw terminals, multi-pole-dual-throw switches havingmultiple (two or more) pole terminals or multi-pole-multi-throw switchescollectively as the selecting switches.

Summing up the functions of the power amplifier of this example, RFsignals having respectively different f1 and f2 and Pout1 and Pout2 canbe transmitted by synchronously switching the first and the secondsingle-pole-dual-throw switches SW1 and SW2 in accordance with thedesired transmission frequencies f1 and f2 or by switching the first andthe second input matching circuits PC1 and PC2 and the second and thethird power amplifiers PA2 and PA3 in accordance with the respectivefrequencies.

There are other types of transmissible systems in which the frequenciesf1 and f2 of the RF signals are in substantially the same band and Pout1and Pout2 respectively corresponding to the frequencies f1 and f2 aredifferent from each other. Such an example is shown in the followingtable.

Communica- f Pout tion type Mode 1 f1 800 MHz Pout1 26 dBm DigitalModulation Mode 2 f2 800 MHz Pout2 31 dBm Analog Modulation Mode 1:spread spectrum (SS) QPSK modulation type Mode 2: FM modulation type

In this table, in the analog FM modulation type in Mode 2, a nonlinearsaturation power amplifier may also be used as a power amplifier and thematching is performed with respect to the second output matching circuitPA303 such that a high power added efficiency and a high harmonicssuppression ratio are obtained at the defined output power of 31 dBm. Onthe other hand, matching is performed with respect to the first outputmatching circuit PA203 such that an adjacent channel leakage power andan intermodulation distortion (IMD: frequency components represented by“mfa±nfb” [where n and m are integers] caused when a plurality ofdifferent signals are amplified) are suppressed to minimal levels and ahigh power added efficiency can be attained at the defined output powerof 26 dBm.

Alternatively, RF signals having substantially equal Pout1 and Pout2 anddifferent f1 and f2 may be transmitted. Such an example is shown in thefollowing table.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.5 GHz Pout2 31 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

EXAMPLE 2

FIGS. 14 to 18 are diagrams illustrating the second example of theswitchable power amplifier according to the present invention. Thisswitchable power amplifier has a function of transmitting RF signalshaving two different frequencies and two different output powers bytemporally synchronizing the switching of the four switches. In thisexample, RF signals having the following exemplary frequencies f and thefollowing exemplary output powers Pout may be transmitted, as shown inthe following table.

Communica- f Pout tion type Mode 1 f1 1.5 GHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.9 GHz Pout2 22 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

FIG. 14 is a configuration diagram of the second example of theswitchable power amplifier according to the present invention.

A first single-pole-dual-throw switch SW1, a first input matchingcircuit PC1 for Mode 1 and a second input matching circuit PC2 for Mode2 are connected to the input side of a first power amplifier PA1. On theother hand, a second single-pole-dual-throw switch SW2, a first outputmatching circuit PC3 for Mode 1 and a second power amplifier PA2 forMode 2 are connected to the output side of the first power amplifierPA1.

The first power amplifier PA1 includes: a first and a second GaAs MESFETPA101 and PA102; a first and a second inter-stage matching circuit PC4and PC5; and a third and a fourth single-pole-dual-throw switch SW3 andSW4. The second power amplifier PA2 includes: a third GaAs MESFET PA201;a third inter-stage matching circuit PA202; and a second output matchingcircuit PA203.

The first, second and third GaAs MESFETs PA101, PA102 and PA201 includedin the first and the second power amplifiers PA1 and PA2 are of adepletion type and have gate widths (Wg) of 1 mm, 4 mm and 30 mm,respectively. The first GaAs MESFETs PA101 having Wg of 1 mm and thefirst single-pole-dual-throw switch SW1 are integrated on a GaAssubstrate (thereby forming a first switch-integrated power amplifierSWPA1), while the second GaAs MESFETs PA102 having Wg of 4 mm and thesecond single-pole-dual-throw switch SW2 are integrated on a GaAssubstrate (thereby forming a second switch-integrated power amplifierSWPA2). Then, the first and the second switch-integrated poweramplifiers SWPA1 and SWPA2 are sealed within resin-molded packages,respectively. On the other hand, the third GaAs MESFET PA201 having Wgof 30 mm is mounted in a ceramic package (mounted on a ceramic carrierand then sealed with a resin).

An integrated circuit including GaAs MESFETs is used as each of thefirst and the second single-pole-dual-throw switches SW1 and SW2. FIG.15 is a circuit diagram of the switches SW1 and SW2. The integratedcircuit using GaAs MESFETs includes: a first parallel GaAs MESFET 1516;a first serial GaAs MESFET 1517; a second parallel GaAs MESFET 1518; asecond serial GaAs MESFET 1519; a first resistance 1520; a secondresistance 1521; a third resistance 1522; and a fourth resistance 1523.By applying control voltages VC1 and VC2, switching is performed betweena third terminal 1503 and a first and a second terminal 1501 and 1502.The GaAs MESFETs have Wg of 1.2 mm.

Each of the third and the fourth single-pole-dual-throw switches SW3 andSW4 may be implemented as a circuit using PIN diodes (i.e., a circuitincluding resin-molded PIN diodes and peripheral circuits thereofincluding C (capacitor) for cutting DC and a choke coil having R(resistance component) or I (inductance component)) or as an integratedcircuit using GaAs MESFETs (i.e., a circuit formed by integrating GaAsMESFETs with peripheral components thereof and molding them with aresin).

FIG. 16 is a circuit diagram of the switches SW3 and SW4. The circuitincluding PIN diodes includes: a first parallel PIN diode 1604; a firstserial PIN diode 1605; a second parallel PIN diode 1606; a second serialPIN diode 1607; a first choke inductance 1608; a second choke inductance1609; a third choke inductance 1610; a first DC blocking capacitor 1611;a second DC blocking capacitor 1612; a third DC blocking capacitor 1613;a first bypass capacitor 1614; and a second bypass capacitor 1615. Byapplying control voltages VC1 and VC2, switching is performed between athird terminal 1603 and a first and a second terminal 1601 and 1602.

The operating power supply voltages of the first, second and third GaAsMESFETs PA101, PA102 and PA201 are as follows. Specifically, the drainvoltages thereof are about 3.5 V and the gate voltages thereof arenegative voltages in the range from about −2.0 V to about −3.0 V. Thefirst GaAs MESFET PA101 is operated while paying much respect to thegain thereof and the second and the third GaAs MESFETs PA102 and PA201are operated in a class AB (with an idle current corresponding to about10% of Idss) while paying much respect to the linearity of theinput/output characteristics and the digital distortion characteristicsthereof. The first, second and third GaAs MESFETs PA101, PA102 and PA201have Idss of about 250 mA, 900 mA and 7.0 A, respectively.

The first and the second single-pole-dual-throw switches SW1 and SW2 areoperated while applying control voltages of 0.0 V/−4.7 V thereto. Whenthe third and the fourth switches SW3 and SW4 are circuits using PINdiodes, these switches are operated while applying control voltages of 0V/12 V thereto. On the other hand, when these switches are circuitsusing GaAs MESFETs, these switches are operated while applying controlvoltages of 0 V/−4.7 V thereto.

In conformity with the implementations described in the first example,the parameters of the first and the second input matching circuits PC1and PC2, the first, second and third inter-stage matching circuits PC4,PC5 and PA202, and the first and the second output matching circuits PC3and PA203 are determined. As a result, the distortion characteristicsrequired for the π/4 shift DQPSK modulation type in this example aresatisfied. The gain and loss levels on the respective stages are asfollows: the output power of the first power amplifier PA1 is about 22.5dBm with respect to an input power of about 0 dBm; a final output powerin Mode 1 is 22 dBm because a power of about 0.5 dBm is lost by thefirst output matching circuit PC3; and a final output power in Mode 2 is31 dBm because of the second power amplifier PA2.

In the above-described respective matching circuits, each of theequivalent circuits thereof can be represented by a combination oflumped constant element components. The first and the second inputmatching circuits PC1 and PC2, the third inter-stage matching circuitPA202 and the first and the second output matching circuits PC3 andPA203 are implemented by using various chip components such as a chipinductor, a chip capacitor and a chip resistor.

FIG. 17 is a configuration diagram of the switchable power amplifier inthe second example. The respective components of the above-describedswitchable power amplifier 124 of this example, the drain voltage/gatevoltage supply sections 125, 126 and 127 for the first, second and thirdGaAs MESFETs PA101, PA102 and PA201 and control voltage supply sections128, 129, 130 and 131 for the first, second, third and fourthsingle-pole-dual-throw switches SW1, SW2, SW3 and SW4 are mounted on aprinted circuit board 132.

Vdd1/Vgg1, Vdd2/Vgg2 and Vdd3/Vgg3 denote the drain voltages/gatevoltages to be supplied to the first, second and third GaAs MESFETsPA101, PA102 and PA201, respectively. VC1, VC2, VC3 and VC4 denote thecontrol voltages to be supplied to the first, second, third and fourthsingle-pole-dual-throw switches SW1, SW2, SW3 and SW4, respectively.

The power supply controls of the drain voltage/gate voltage supplysections (or power supply controllers) 125, 126 and 127 are performed inassociation with those of the control voltage supply sections (orfeeders) 128, 129, 130 and 131 for the first, second, third and fourthsingle-pole-dual-throw switches SW1, SW2, SW3 and SW4. For example, whenPout1 is selected as the output, the feeders are controlled such thatSW1 selects Pin1, SW3 and SW4 select PC4 and SW2 select Pout1. The drainvoltage/gate voltage supply section 127 is controlled such that theunused PA201 is deactivated for reducing the power consumption.

The drain voltage/gate voltage supply section is implemented by using achip inductor as a choke and a bypass capacitor or by using a microstripline for mounting a switchable power amplifier on a printed circuitboard and a bypass capacitor.

It is noted that, when the output powers defined in Modes 1 and 2 aredifferent as in this example or when the transmission/receptionconditions of the RF signals are variable, it is necessary to vary orstabilize the output powers. Thus, since a gain control function forstabilizing an output power and holding a constant power isindispensable as a function of a transmission power amplifier, anattenuator or a power amplifier having an auto gain control (AGC)function or an auto level control (ALC) function is integrated into thepower amplifier, thereby feedbacking and controlling the monitoredoutput power. The output power can be monitored by a capacitancecoupling or a directional coupler (as to exemplary configurations, seeFIGS. 5 and 6 in the first example).

By integrating the RF section 120, the IF signal processing section 121and the base band section 122, which are shown in the block diagram ofan information communication unit in FIG. 7 in the first example, on atleast one printed circuit board (e.g., a dielectric substrate or thelike) so as to include the switchable power amplifier 124 of thisexample and collectively mounting them into the case of an informationcommunication unit, the unit can be downsized at lower costs as comparedwith a conventional example. As a result, a highly value-addedinformation communication terminal unit commonly applicable to systemshaving different frequency bands, transmission output powers andmodulation types can be obtained.

As specific exemplary implementations of the information communicationunit, the implementations shown in FIGS. 8 to 10 in the first example(i.e, an implementation in which switches for switchingtransmission/reception for Modes 1 and 2 are connected to the switchablepower amplifier and an implementation in which switches for performingdiversity transmission/reception is connected thereto) are usable. Byutilizing these implementations, the transmission and reception can beperformed with respect to Modes 1 and 2.

Alternatively, as shown in FIG. 11 in the first example, by commonlyusing a single antenna section in Modes 1 and 2 and connecting theswitch for switching the output powers of the switchable power amplifierfor Modes 1 and 2 to the switch for switching transmission andreception, the transmission and reception can also be performed withrespect to Modes 1 and 2.

It is noted that the switchable power amplifier of this example may alsobe implemented under the following configurations. FIG. 18 is a diagramshowing ranges implemented as MMICs in this example. The followingdescriptions (182) to (185) correspond to the reference numeralsattached to the broken line portions shown in FIG. 18. The followingMMIC implementations described in (182) to (185) are representativepractical ones in respect of the costs, the production yield of a chipand the like. However, the implementations are not limited thereto, butinclude the exemplary configurations and mounting methods of hybrid ICsand MMICs as described in the first example. (181): Implement GaAsMESFETs, single-pole-dual-throw switches, matching circuits and otherperipheral circuits as hybrid ICs. Seal the GaAs MESFETs having Wg of 1mm and 4 mm within resin-molded packages.

(182): Integrate at least one of the third single-pole-dual-throw switchSW3, the first and the second input matching circuits PC1 and PC2 andthe first and the second inter-stage matching circuits PC4 and PC5 intothe first switch-integrated power amplifier SWPA1 and mold them with aresin.

(183): Integrate at least one of the fourth single-pole-dual-throwswitch SW4, the first output matching circuit PC3 and the thirdinter-stage matching circuit PA202 into the second switch-integratedpower amplifier SWPA2 and mold them with a resin.

(184): Integrate the second single-pole-dual-throw switch SW2 and thesecond power amplifier PA2 on a GaAs substrate and mold them with aresin.

(185): Integrate the second GaAs MESFET PA102 and the second poweramplifier PA2 on a GaAs substrate and mold them with a resin.

In these implementations (182) to (185), a matching circuit implementedas an MMIC has a combination of microstrip lines, spiral inductors, MIM(metal-insulator-metal) capacitors, comb capacitors, thin-filmresistances (such as NiCr) and the like on a GaAs substrate. On theother hand, the components not implemented within an MMIC areindividually mounted on a printed circuit board.

It is noted that an MMIC implementation includes implementing the firstor the second power amplifier PA1 and PA2 as an MMIC and selectivelyimplementing the components of each power amplifier (active elements,passive circuits and the like) as an MMIC (e.g., implementing all thecomponents of the second power amplifier PA2 other than the outputmatching circuit thereof as an MMIC).

It is also noted that not only the GaAs MESFETs used as the activeelements for the above-described power amplifier but also other activeelements such as enhanced GaAs MESFETs and transistors (e.g., MOSFETs,HBTs, HEMTs, etc.) formed on another semiconductor substrate may beused.

Moreover, a portable unit is currently supposed to satisfy theoperational requirements about an operating voltage of 3.0 V to 3.4 Vcorresponding to that of three NiCd cells or a single Li ion cell.Though the operating power supply voltage of the GaAs MESFET of thisexample is 3.5 V, the operating voltage of any other logic IC may beused. Alternatively, depending upon the type of an informationcommunication unit in question, the power supply voltage may be set atother values. If optimum active elements operating within the definedvoltage range are used, the present example may be implemented at anoperating voltage other than 3.5 V.

Furthermore, in this example, a negative voltage generated by a DC-DCconverter is used as the gate voltage of the GaAs MESFET. The presentexample may also be implemented by selecting active elements operatingby a single positive power supply so as to eliminate a negative powersupply.

The first and the second power amplifiers PA1 and PA2 in this exampleare single-stage amplifiers. Alternatively, multi-stage amplifiers mayalso be used instead. For example, a driver power amplifier may beadditionally provided on the input side of the first power amplifier.

In this example, matching circuits used as passive circuit components ofa power amplifier have been particularly described. Applicable matchingcircuits are not limited to passive components having a matchingfunction, but include various kinds of passive circuits such as a chokeinductor on a power supply line, a bypass capacitor, divided resistancesfor applying a bias, a filter, a harmonic trap circuit and anattenuator. For example, a choke inductor on a power supply line, abypass capacitor and divided resistances for applying a bias may beincluded within a power amplifier implemented as an MMIC. As for afilter, if the transmission frequency and the reception frequency of anRF signal are different from each other, a band-pass filter having apredetermined pass band width may be inserted subsequent to an outputmatching circuit or a harmonic trap circuit may be inserted into theoutput matching circuit.

In this example, RF signals corresponding to two types are transmittedby using single-pole-dual-throw switches. However, a desired poweramplifier and a desired information communication unit may be formedeven by the use of single-pole-multi-throw switches having multiple(three or more) throw terminals, multi-pole-dual-throw switches havingmultiple (two or more) pole terminals or multi-pole-multi-throw switchescollectively as the selecting switches.

The switchable power amplifier may be implemented not only under theabove-described specifications but also under the followingspecifications.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.9 GHz Pout2 22 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

Communica- f Pout tion type Mode 1 f1 1.9 GHz Pout1 22 dBm DigitalModulation Mode 2 f2 900 MHz Pout2 31 dBm Analog Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: FM modulation type

In the latter specifications, in the analog FM modulation type in Mode2, a nonlinear saturation power amplifier may also be used as a poweramplifier and matching is performed with respect to the second outputmatching circuit PA203 such that a high power added efficiency and ahigh harmonics suppression ratio are obtained at the defined outputpower of 31 dBm. On the other hand, matching is performed with respectto the first output matching circuit PC3 such that an adjacent channelleakage power is suppressed to minimal levels and a high power addedefficiency can be attained at the defined output power of 22 dBm.

EXAMPLE 3

FIGS. 21 to 24 are diagrams illustrating the third example of theswitchable power amplifier according to the present invention. Thisswitchable power amplifier has a function of transmitting RF signalshaving two different frequencies and two different output powers byusing a wide-band power amplifier as a driver power amplifier (or driveramp) of the power amplifier on the final output stage and temporallysynchronizing the switching of the switch.

Such a “wide-band power amplifier” generally refers to a power amplifierexhibiting flat characteristics over a frequency range covering two ormore desired frequency bands and satisfying desired characteristics.FIG. 19 is a graph illustrating a 3 dB band width. As shown in FIG. 19,the 3 dB band width (Δf) of the gain is defined so as to include adesired frequency range (from a frequency f1 to a frequency f2).Hereinafter, the 3 dB band width (Δf) of the gain will be assumed toinclude a range from about 800 MHz to about 2.5 GHz. In the case wheresome variation is caused in the flat portion of the frequencycharacteristics shown in FIG. 19, an average value in the flat portion(such a value is generally referred to as a “Typ. value”) is obtainedand the range defined between the value to −3 dB of the value is assumedto be Δf.

In addition, a power amplifier having gain characteristics having peaksin at least two desired frequency bands (i.e., a so-called“multi-frequency matching power amplifier”) can be used as a poweramplifier substantially equivalent to a wide-band power amplifier. FIG.20 is a graph illustrating a 3 dB band width of an amplifier having twopeaks. As shown in FIG. 20, in the case of a dual-frequency matchingpower amplifier, the two 3 dB bands (Δf1 and Δf2) corresponding to thegains at the two peaks (i.e., a first peak P1 and a second peak P2) ofthe gain characteristics thereof are defined so as to include the twodesired frequencies f1 and f2, respectively.

By using such a wide-band power amplifier, the input matching circuitsand redundant switches which are required in the first and the secondexamples can be eliminated, thereby obtaining a smaller-sizedhigher-performance switchable power amplifier.

Consider a case of transmitting RF signals having the followingfrequencies f and the following output powers Pout as shown in thefollowing table.

Communica- f Pout tion type Mode 1 f1 1.9 GHz Pout1 22 dBm DigitalModulation Mode 2 f2 2.4 GHz Pout2 26 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: spread spectrum (SS) QPSK modulationtype

FIG. 21 is a configuration diagram illustrating the third example of theswitchable power amplifier according to the present invention.

A first single-pole-dual-throw switch SW1, a second power amplifier PA2for Mode 1 and a third power amplifier PA3 for Mode 2 are connected tothe output side of a first power amplifier PA1.

The first power amplifier PA1 includes a first and GaAs MESFET PA101.The second power amplifier PA2 includes: a second GaAs MESFET PA201; afirst inter-stage matching circuit PA202; and a first output matchingcircuit PA203. The third power amplifier PA3 includes: a third GaAsMESFET PA301; a second inter-stage matching circuit PA302; and a secondoutput matching circuit PA303.

The first, second and third GaAs MESFETs PA101, PA201 and PA301 includedin the first, second and third power amplifiers PA1, PA2 and PA3 are ofa depletion type and have gate widths (Wg) of 1 mm, 4 mm and 8 mm,respectively.

The first GaAs MESFETs PA101 having Wg of 1 mm and the firstsingle-pole-dual-throw switch SW1 are integrated on a GaAs substrate(thereby forming a first switch-integrated power amplifier SWPA1). Thesecond GaAs MESFETs PA201 having Wg of 4 mm, the first inter-stagematching circuit PA202 and the first output matching circuit PA203 areintegrated on a GaAs substrate (thereby forming a first integrated poweramplifier MMPA1). The third GaAs MESFETs PA301 having Wg of 8 mm, thesecond inter-stage matching circuit PA302 and the second output matchingcircuit PA303 are integrated on a GaAs substrate (thereby forming asecond integrated power amplifier MMPA2). Then, the first, second andthird power amplifiers SWPA1, MMPA1 and MMPA2 are sealed withinresin-molded packages, respectively.

An integrated circuit including a GaAs MESFET is used as the firstsingle-pole-dual-throw switch SW1 (as to an exemplary circuitconfiguration, see FIG. 15 in the second example).

The operating power supply voltages of the first, second and third GaAsMESFETs PA101, PA201 and PA301 are as follows. Specifically, the drainvoltages thereof are 3.5 V and the gate voltages thereof are negativevoltages in the range from about −2.0 V to about −3.0 V. The first GaAsMESFET PA101 is operated while paying much respect to the gain thereofand the second and the third GaAs MESFETs PA201 and PA301 are operatedin a class AB (with an idle current corresponding to about 10% of Idss)while paying much respect to the linearity of the input/outputcharacteristics and the digital distortion characteristics thereof. Thefirst, second and third GaAs MESFETs PA101, PA201 and PA301 have Idss ofabout 250 mA, about 900 mA and about 1.7 A, respectively. On the otherhand, the first single-pole-dual-throw switch SW1 is operated whileapplying control voltages of 0 V and −4.7 V thereto.

In the switchable power amplifier of this example, by using a wide-bandpower amplifier as the first power amplifier PA1, an input matchingcircuit and a switch for switching the input matching circuit which isrequired in the first and the second examples can be eliminated. Ingeneral, the below-described method is mainly used for realizing awide-band operation of such a power amplifier. FIGS. 22(a) to 22(d) arediagrams illustrating the wide-band operation of a power amplifier. InFIG. 22, the reference numeral 2201 denotes an active element (MESFET),2202 denotes an output terminal and 2203 denotes an input terminal.

(1) Insert a serial circuit including a resistance 2204 and a capacitor2205 as a negative feedback circuit β to between the output terminal(drain terminal) 2202 and the input terminal (gate terminal) 2203 of theactive element FET 2201 (FIG. 22(a)).

(2) Insert an attenuator 2206 in a π-shape or a T-shape (formed by afirst, a second and a third resistance R1, R2 and R3) to the input sideof the active element 2201 (FIG. 22(b)).

(3) Insert a resistance 2207 (50 Ω) in parallel to the input side of theactive element 2201 (FIG. 22(c)).

(4) Insert a first and a second impedance converter 2208 and 2209 (orconstant resistance circuits) enabling a matching in a wide band to theinput side and the output side of the active element, respectively.

In this example, the wide-band power amplifier shown in FIG. 22(a) isused. The resistance 2204 and the capacitor 2205 of the negativefeedback circuit of the first power amplifier PA1 are integrated withthe first switch-integrated power amplifier SWPA1 and then sealed withina resin-molded package.

In determining the parameters of the matching circuits, those of thefirst and the second inter-stage matching circuits PA202 and PA302 aredetermined in view of a matching between the output impedances of thefirst GaAs MESFET PA101 and the input impedances of the second and thethird GaAs MESFETs PA201 and PA301 at the frequencies f1 and f2. Inconformity with the implementations of the matching circuits describedin the first example, the parameters of the first and the second outputmatching circuits PA203 and PA303 are optimized. As a result, thedistortion characteristics required for the π/4 shift DQPSK modulationtype and the spread spectrum (SS) QPSK modulation type in this exampleare satisfied.

In each of the matching circuits, the equivalent circuit thereof isrepresented by a combination of lumped constant element components. Eachof the first and the second inter-stage matching circuits PA202 andPA302 and the first and the second output matching circuits PA203 andPA303 is represented by a combination of a microstrip line, a spiralinductor, an MIM (metal-insulator-metal) capacitor, a comb capacitor, athin-film resistance (such as NiCr) and the like on a GaAs substrate.

FIG. 23 is a configuration diagram of the switchable power amplifier inthe third example. The respective components of the above-describedswitchable power amplifier 110 of this example, the drain voltage/gatevoltage supply sections 111, 112 and 113 for the first, second and thirdGaAs MESFETs PA101, PA201 and PA301 and control voltage supply section114 for the first single-pole-dual-throw switch SW1 are mounted on aprinted circuit board 115.

Vdd1/Vgg1, Vdd2/Vgg2 and Vdd3/Vgg3 denote the drain voltages/gatevoltages to be supplied to the first, second and third GaAs MESFETsPA101, PA201 and PA301, respectively. VC1 denotes the control voltage tobe supplied to the first single-pole-dual-throw switch SW1.

The power supply controls of the drain voltage/gate voltage supplysections (or power supply controllers) 111, 112 and 113 are performed inassociation with that of the control voltage supply section (or feeder)114 for the first single-pole-dual-throw switch SW1. For example, whenPout1 is selected as the output, the feeder is controlled such that SW1selects Pout1. The drain voltage/gate voltage supply section 113 iscontrolled such that the unused PA301 is deactivated for reducing thepower consumption.

The drain voltage/gate voltage supply section is implemented by a chipinductor as a choke and a bypass capacitor or by a microstrip line formounting a switchable power amplifier on a printed circuit board and abypass capacitor.

It is noted that, when the output powers defined in Modes 1 and 2 aredifferent as in this example or when the transmission/receptionconditions of the RF signals are variable, it is necessary to vary orstabilize the output powers. Thus, since a gain control function forstabilizing an output power and holding a constant power isindispensable as a function of a transmission power amplifier, anattenuator or a power amplifier having an auto gain control (AGC) or anauto level control (ALC) function is integrated into the poweramplifier, thereby feedbacking and controlling the monitored outputpower. The output power can be monitored by a capacitance coupling or adirectional coupler (as to exemplary configurations, see FIGS. 5 and 6in the first example).

By integrating the RF section 120, the IF signal processing section 121and the base band section 122, which are shown in the block diagram ofan information communication unit in FIG. 7 in the first example, on atleast one printed circuit board (e.g., a dielectric substrate or thelike) so as to include the switchable power amplifier 110 of thisexample and collectively mounting them into the case of an informationcommunication unit, the unit can be downsized at lower costs as comparedwith a conventional example. As a result, a highly value-addedinformation communication terminal unit commonly applicable to systemshaving different frequency bands, transmission output powers andmodulation types can be obtained.

As specific exemplary implementations of the information communicationunit, the implementations shown in FIGS. 8 to 10 in the first example(i.e, an implementation in which switches for switchingtransmission/reception for Modes 1 and 2 are connected to the switchablepower amplifier and an implementation in which switches for performingdiversity transmission/reception is connected thereto) are usable. Byutilizing these implementations, the transmission and reception can beperformed with respect to Modes 1 and 2.

Alternatively, as shown in FIG. 11 in the first example, by commonlyusing a single antenna section in Modes 1 and 2 and connecting theswitch for switching the output powers of the switchable power amplifierfor Modes 1 and 2 to the switch for switching transmission andreception, the transmission and reception can also be performed withrespect to Modes 1 and 2.

It is noted that the switchable power amplifier of this example may alsobe implemented under the following specific configurations. FIGS. 24(a)to 24(d) are diagrams showing parts implemented as MMICs in the thirdexample. The following descriptions (242) to (245) correspond to thereference numerals 242 to 245 attached to the broken line portions shownin FIG. 24. The following MMIC implementations described in (242) to(245) are representative practical ones in respects of the costs, theproduction yield of a chip and the like. However, the implementationsare not limited thereto, but include the exemplary configurations andmounting methods of hybrid ICs and MMICs as described in the firstexample.

(241): Implement GaAs MESFETs, a single-pole-dual-throw switch, matchingcircuits and other peripheral circuits as hybrid ICs. The GaAs MESFETshaving Wg of 1 mm and 4 mm are sealed within resin-molded packages,while the GaAs MESFET having Wg of 8 mm is mounted in a ceramic package(i.e., mounted on a ceramic carrier and then sealed with a resin).Various chip components such as a chip inductor, a chip capacitor and achip resistor are used as the matching circuits.

(242): Integrate at least one of the first integrated power amplifierMMPA1 and the second integrated power amplifier MMPA2 into the firstswitch-integrated power amplifier SWPA1.

(243): Integrate at least one of the part of the second power amplifierPA2 excluding the first output matching circuit PA203 and the part ofthe third power amplifier PA3 excluding the second output matchingcircuit PA303 into the first switch-integrated power amplifier SWPA1.

(244): Integrate the first single-pole-dual-throw switch SW1 with atleast one of the second power amplifier PA2 and the third poweramplifier PA3 on a GaAs substrate.

(245): Integrate the first power amplifier PA1 with at least one of thesecond power amplifier PA2 and the third power amplifier PA3 on a GaAssubstrate.

In (242) to (245), a chip implemented as an MMIC has been sealed withina resin-molded package or mounted in a bare chip manner, and a matchingcircuit implemented as an MMIC include a combination of a microstripline, a spiral inductor, an MIM (metal-insulator-metal) capacitor, acomb capacitor, a thin-film resistance (such as NiCr) and the like on aGaAs substrate. On the other hand, the components not implemented withinan MMIC are individually mounted on a printed circuit board.

It is noted that an MMIC implementation includes implementing the first,second or third power amplifier PA1, PA2 or PA3 as an MMIC andselectively implementing the components of each power amplifier (activeelements, passive circuits and the like) as an MMIC (e.g., implementingall the components of the first or the second power amplifier PA1 or PA2other than the output matching circuit thereof as an MMIC).

It is also noted that not only the GaAs MESFETs used as the activeelements for the above-described power amplifier but also other activeelements such as enhanced GaAs MESFETs and transistors (e.g., MOSFETs,HBTs, HEMTs, etc.) formed on another semiconductor substrate may beused.

Moreover, a portable unit is currently supposed to satisfy theoperational requirements about an operating voltage of 3.0 V to 3.4 Vcorresponding to that of three NiCd cells or a single Li ion cell.Though the operating power supply voltage of the GaAs MESFET of thisexample is 3.5 V, the operating voltage of any other logic IC may beused. Alternatively, depending upon the type of an informationcommunication unit in question, the power supply voltage may be set atother values. If optimum active elements operating within the definedvoltage range are used, the present example may be implemented at anoperating voltage other than 3.5 V.

Furthermore, in this example, a negative voltage generated by a DC-DCconverter is used as the gate voltage of the GaAs MESFET. The presentexample may also be implemented by selecting active elements operatingby a single positive power supply so as to eliminate a negative powersupply.

The first, second and third power amplifiers PA1, PA2 and PA3 in thisexample are single-stage amplifiers. Alternatively, multi-stageamplifiers may also be used instead. For example, a driver poweramplifier may be additionally provided on the input side of the firstpower amplifier.

In this example, matching circuits used as passive circuit components ofa power amplifier have been particularly described. Applicable matchingcircuits are not limited to passive components having a matchingfunction, but include various kinds of passive circuits such as a chokeinductor on a power supply line, a bypass capacitor, divided resistancesfor applying a bias, a filter, a harmonic trap circuit and anattenuator. For example, a choke inductor on a power supply line, abypass capacitor and divided resistances for applying a bias may beincluded within a power amplifier implemented as an MMIC. As for afilter, if the transmission frequency and the reception frequency of anRF signal are different from each other, a band-pass filter having apredetermined pass band width may be inserted subsequent to an outputmatching circuit or a harmonic trap circuit may be inserted into theoutput matching circuit.

In this example, RF signals corresponding to two types are transmittedby using a single-pole-dual-throw switch. However, a desired poweramplifier and a desired information communication unit may be formedeven by the use of a single-pole-multi-throw switch having multiple(three or more) throw terminals, a multi-pole-dual-throw switch havingmultiple (two or more) pole terminals or a multi-pole-multi-throw switchcollectively as the selecting switch.

EXAMPLE 4

FIGS. 25 and 26 are diagrams illustrating the fourth example of theswitchable power amplifier according to the present invention. Thisswitchable power amplifier has a function of transmitting RF signalshaving two different frequencies and two different output powers byusing wide-band power amplifiers as a driver power amplifier (or driveramp) of the power amplifier on the final output stage and a pre-driverpower amplifier (or pre-driver amp) and temporally synchronizing theswitching of the respective switches. The power amplifier defined withreference to FIG. 19 and 20 in the third example is used as thewide-band power amplifier (including the above-described multi-frequencymatching power amplifier). By using such a wide-band power amplifier,the input matching circuits and redundant switches which are required inthe first and the second examples can be eliminated, thereby obtaining asmaller-sized higher-performance switchable power amplifier.

The power amplifier of this example transmits RF signals having thefollowing frequencies f and the following output powers Pout as shown inthe following table.

Communica- f Pout tion type Mode 1 f1 1.9 GHz Pout1 22 dBm DigitalModulation Mode 2 f2 2.4 GHz Pout2 26 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: spread spectrum (SS) QPSK modulationtype

FIG. 25 is a configuration diagram of the switchable power amplifier inthe fourth example of the present invention. A second power amplifierPA2 for Mode 1 and a third power amplifier PA3 for Mode 2 are connectedto the output side of a first power amplifier PA1 via a firstsingle-pole-dual-throw switch SW1.

The first power amplifier PA1 includes: a first GaAs MESFET PA101; afirst inter-stage matching circuit PA103; and a second GaAs MESFETPA102. The second power amplifier PA2 includes: a third GaAs MESFETPA201; a second inter-stage matching circuit PA202; and a first outputmatching circuit PA203. The third power amplifier PA3 includes: a fourthGaAs MESFET PA301; a third inter-stage matching circuit PA302; and asecond output matching circuit PA303.

The first and the second GaAs MESFETs PA101 and PA102 of the first poweramplifier PA1, the third GaAs MESFET PA201 of the second power amplifierPA2 and the fourth GaAs MESFET PA301 of the third power amplifier PA3are of a depletion type and have gate widths (Wg) of 0.6 mm, 2 mm, 4 mmand 8 mm, respectively.

The first power amplifier PA1 and the first single-pole-dual-throwswitch SWl are integrated on a GaAs substrate (thereby forming a firstswitch-integrated power amplifier SWPA1). The components of the secondpower amplifier PA2 or the third GaAs MESFETs PA201, the secondinter-stage matching circuit PA202 and the first output matching circuitPA203 are integrated on a GaAs substrate (thereby forming a firstintegrated power amplifier MMPA1). The components of the third poweramplifier PA3 or the fourth GaAs MESFETs PA301, the third inter-stagematching circuit PA302 and the second output matching circuit PA303 areintegrated on a GaAs substrate (thereby forming a second integratedpower amplifier MMPA2). Then, the first, second and third poweramplifiers SWPA1, MMPA1 and MMPA2 are sealed within resin-moldedpackages, respectively.

An integrated circuit including a GaAs MESFET is used as the firstsingle-pole-dual-throw switch SW1 (as to an exemplary circuitconfiguration, see FIG. 15 in the second example).

The operating power supply voltages of the first, second, third andfourth GaAs MESFETs PA101, PA102, PA201 and PA301 are as follows.Specifically, the drain voltages thereof are about 3.5 V and the gatevoltages thereof are negative voltages in the range from −2.0 V to −3.0V. The first and the second GaAs MESFETs PA101 and PA102 are operatedwhile paying much respect to the gain thereof and the third and thefourth GaAs MESFETs PA201 and PA301 are operated in a class AB (with anidle current corresponding to about 10% of Idss) while paying muchrespect to the linearity of the input/output characteristics and thedigital distortion characteristics thereof. The GaAs MESFETs PA101,PA102, PA201 and PA301 have Idss of about 160 mA, about 550 mA, about900 mA and about 1.7 A, respectively.

On the other hand, the first single-pole-dual-throw switch SW1 isoperated while applying control voltages of 0 V and −4.7 V thereto.

In the switchable power amplifier of this example, by using wide-bandpower amplifiers as the first and the second power amplifiers PA1 andPA2, an input matching circuit and a switch for switching the inputmatching circuit which is required in the first and the second examplescan be eliminated.

In general, the four types of methods shown in FIGS. 22(a) to 22(d) inthe third example are used for realizing a wide-band operation of such apower amplifier. In this example, the method shown in FIG. 22(a) inwhich a negative feedback circuit or a serial circuit including aresistance and a capacitor is inserted to between the input and theoutput of the GaAs MESFET is used.

The resistance and the capacitor of the negative feedback circuit ofeach of the first and the second GaAs MESFETs PA101 and PA102 areintegrated with the first switch-integrated power amplifier SWPA1 andthen sealed within a resin-molded package.

In determining the parameters of the matching circuits, those of thesecond and the third inter-stage matching circuits PA202 and PA302 aredetermined in view of a matching between the output impedances of thesecond GaAs MESFET PA102 and the input impedances of the third and thefourth GaAs MESFETs PA201 and PA301 at the frequencies f1 and f2. Thefirst inter-stage matching circuit PA103 within the firstswitch-integrated power amplifier SWPA1 is implemented by a couplingcapacitor so as to perform a multi-stage RF coupling (or to block the DCcomponents). The first inter-stage matching circuit PA103 may also be apassive circuit including lumped constant elements. In conformity withthe implementations of the matching circuits described in the firstexample, the parameters of the first and the second output matchingcircuits PA203 and PA303 are determined. As a result, the distortioncharacteristics required for the π/4 shift DQPSK modulation type and thespread spectrum (SS) QPSK modulation type in this example are satisfied.

In each of the matching circuits, the equivalent circuit thereof isrepresented by a combination of lumped constant element components. Eachof the second and the third inter-stage matching circuits PA202 andPA302 and the first and the second output matching circuits PA203 andPA303 is formed by a combination of a microstrip line, a spiralinductor, an MIM (metal-insulator-metal) capacitor, a comb capacitor, athin-film resistance (such as NiCr) and the like on a GaAs substrate.

FIG. 26 is a configuration diagram of the switchable power amplifier inthe fourth example. The respective components of the above-describedswitchable power amplifier 101 of this example, the drain voltage/gatevoltage supply section 102 for the first and the second GaAs MESFETsPA101 and PA102, the drain voltage/gate voltage supply sections 103 and104 for the third and the fourth GaAs MESFETs PA201 and PA301 and thecontrol voltage supply section 105 for the first single-pole-dual-throwswitch SW1 are mounted on a printed circuit board 106.

Vdd1/Vgg1 denote the drain voltage/gate voltage to be supplied to thefirst and the second GaAs MESFETs PA101 and PA102. Vdd2/Vgg2 andVdd3/Vgg3 denote the drain voltages/gate voltages to be supplied to thethird and the fourth GaAs MESFETs PA201 and PA301, respectively. VC1denotes the control voltage to be supplied to the firstsingle-pole-dual-throw switch SW1.

The power supply controls of the drain voltage/gate voltage supplysections (or power supply controllers) 102, 103 and 104 are performed inassociation with that of the control voltage supply section (or feeder)105 for the first single-pole-dual-throw switch SW1. For example, whenPout1 is selected as the output, the feeder is controlled such that SW1selects Pout1. The drain voltage/gate voltage supply section 104 iscontrolled such that the unused PA301 is deactivated for reducing thepower consumption.

The drain voltage/gate voltage supply section is implemented by a chipinductor as a choke and a bypass capacitor or by a microstrip line formounting a switchable power amplifier on a printed circuit board and abypass capacitor.

It is noted that, when the output powers defined in Modes 1 and 2 aredifferent as in this example or when the transmission/receptionconditions of the RF signals are variable, it is necessary to vary orstabilize the output powers. Thus, since a gain control function forstabilizing an output power and holding a constant power isindispensable as a function of a transmission power amplifier, anattenuator or a power amplifier having an auto gain control (AGC) or anauto level control (ALC) function is integrated into the poweramplifier, thereby feedbacking and controlling the monitored outputpower. The output power can be monitored by a capacitance coupling or adirectional coupler (as to exemplary configurations, see FIGS. 5 and 6in the first example).

By integrating the RF section 120, the IF signal processing section 121and the base band section 122, which are shown in the block diagram ofan information communication unit in FIG. 7 in the first example, on atleast one printed circuit board (e.g., a dielectric substrate or thelike) so as to include the switchable power amplifier 101 of thisexample and collectively mounting them into the case of an informationcommunication unit, the unit can be downsized at lower costs as comparedwith a conventional example. As a result, a highly value-addedinformation communication terminal unit commonly applicable to systemshaving different frequency bands, transmission output powers andmodulation types can be obtained.

As specific exemplary implementations of the information communicationunit, the implementations shown in FIGS. 8 to 10 in the first example(i.e, an implementation in which switches for switchingtransmission/reception for Modes 1 and 2 are connected to the switchablepower amplifier and an implementation in which switches for performingdiversity transmission/reception is connected thereto) are usable. Byutilizing these implementations, the transmission and reception can beperformed with respect to Modes 1 and 2.

Alternatively, as shown in FIG. 11 in the first example, by commonlyusing a single antenna section in Modes 1 and 2 and connecting theswitch for switching the output powers of the switchable power amplifierfor Modes 1 and 2 to the switch for switching transmission andreception, the transmission and reception can also be performed withrespect to Modes 1 and 2.

It is noted that the switchable power amplifier of this example may alsobe implemented under the following specific configurations. Thefollowing MMIC implementations described in (272) to (276) arerepresentative practical ones in respects of the costs, the productionyield of a chip and the like. However, the implementations are notlimited thereto, but include the exemplary configurations and mountingmethods of hybrid ICs and MMICs as described in the first example. FIGS.27(a) to 27(d) are diagrams showing parts to be implemented as MMICs inthe fourth example. The following descriptions (272) to (276) correspondto the reference numerals attached to the broken line portions shown inFIG. 27.

(271): Implement GaAs MESFETs, switches, matching circuits and otherperipheral circuits as hybrid ICs. The GaAs MESFETs having Wg of 1 mmand 4 mm are sealed within resin-molded packages, while the GaAs MESFEThaving Wg of 8 mm is mounted in a ceramic package (i.e., mounted on aceramic carrier and then sealed with a resin). Various chip componentssuch as a chip inductor, a chip capacitor and a chip resistor are usedas the matching circuits.

(272): Integrate at least one of the first integrated power amplifierMMPA1 and the second integrated power amplifier MMPA2 into the firstswitch-integrated power amplifier SWPA1.

(273): Integrate at least one of the part of the second power amplifierPA2 excluding the first output matching circuit PA203 and the part ofthe third power amplifier PA3 excluding the second output matchingcircuit PA303 into the first switch-integrated power amplifier SWPA1.

(274): Integrate the first single-pole-dual-throw switch SW1 with atleast one of the second power amplifier PA2 and the third poweramplifier PA3 on a GaAs substrate.

(275): Integrate the first power amplifier PA1 with at least one of thesecond power amplifier PA2 and the third power amplifier PA3 on a GaAssubstrate.

(276): Form multiple chips including a chip formed by integrating thefirst single-pole-dual-throw switch SW1 with at least one of the secondpower amplifier PA2 and the third power amplifier PA3 on a GaAssubstrate and a chip formed by integrating the first power amplifier PA1on the GaAs substrate. Mounting is performed by introducing the multiplechips into a package or connecting the multiple chips onto a printedcircuit board in a bare chip manner.

In (274) to (276), a chip implemented as an MMIC has been sealed withina resin-molded package or mounted in a bare chip manner, and each of thematching circuits implemented within an MMIC includes a combination of amicrostrip line, a spiral inductor, an MIM (metal-insulator-metal)capacitor, a comb capacitor, a thin-film resistance (such as NiCr) andthe like on a GaAs substrate. On the other hand, the components notimplemented within the MMIC are individually mounted on a printedcircuit board.

It is noted that an MMIC implementation includes implementing the first,second or third power amplifier PA1, PA2 or PA3 as an MMIC andselectively implementing the components of each power amplifier (activeelements, passive circuits and the like) as an MMIC (e.g., implementingall the components of the second or the third power amplifier PA2 or PA3other than the output matching circuit thereof as an MMIC). It is alsonoted that not only the GaAs MESFETs used as the active elements for theabove-described power amplifier but also other active elements such asenhanced GaAs MESFETs and transistors (e.g., MOSFETs, HBTs, HEMTs, etc.)formed on another semiconductor substrate may be used.

Moreover, a portable unit is currently supposed to satisfy theoperational requirements about an operating voltage of 3.0 V to 3.4 Vcorresponding to that of three NiCd cells or a single Li ion cell.Though the operating power supply voltage of the GaAs MESFET of thisexample is 3.5 V, the operating voltage of any other logic IC may beused. Alternatively, depending upon the type of an informationcommunication unit in question, the power supply voltage may be set atother values. If optimum active elements operating within the definedvoltage range are used, the present example may be implemented at anoperating voltage other than 3.5 V.

Furthermore, in this example, a negative voltage generated by a DC-DCconverter is used as the gate voltage of the GaAs MESFET. The presentexample may also be implemented by selecting active elements operatingby a single positive power supply so as to eliminate a negative powersupply.

The second and the third power amplifiers PA2 and PA3 in this exampleare single-stage amplifiers. Alternatively, multi-stage amplifiers likethe first power amplifier PA1 may also be used instead.

In this example, matching circuits used as passive circuit components ofa power amplifier have been particularly described. Applicable matchingcircuits are not limited to passive components having a matchingfunction, but include various kinds of passive circuits such as a chokeinductor on a power supply line, a bypass capacitor, divided resistancesfor applying a bias, a filter, a harmonic trap circuit and anattenuator. For example, a choke inductor on a power supply line, abypass capacitor and divided resistances for applying a bias may beincluded within a power amplifier implemented as an MMIC. As for afilter, if the transmission frequency and the reception frequency of anRF signal are different from each other, a band-pass filter having apredetermined pass band width may be inserted subsequent to an outputmatching circuit or a harmonic trap circuit may be inserted into theoutput matching circuit.

In this example, RF signals corresponding to two types are transmittedby using a single-pole-dual-throw switch. However, a desired poweramplifier and a desired information communication unit may be formedeven by the use of a single-pole-multi-throw switch having multiple(three or more) throw terminals, a multi-pole-dual-throw switch havingmultiple (two or more) pole terminals or a multi-pole-multi-throw switchcollectively as the selecting switch.

The power amplifier of this example can be implemented not only underthe above-described specifications but also under the followingspecifications.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm AnalogModulation Mode 2 f2 1.5 GHz Pout2 31 dBm Digital Modulation Mode 1: FMmodulation type Mode 2: π/4 shift DQPSK modulation type

Moreover, RF signals having substantially equal Pout1 and Pout 2 anddifferent f1 and f2 may be transmitted. For example, the following RFsignals may be transmitted.

Communica- f Pout tion type Mode 1 f1 900 GHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.5 GHz Pout2 31 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

EXAMPLE 5

FIGS. 28 to 30 are diagrams illustrating the fifth example of theswitchable power amplifier according to the present invention. Thisswitchable power amplifier has a function of transmitting RF signalshaving two different frequencies and two different output powers byusing wide-band power amplifiers as a driver power amplifier (or driveramp) of the power amplifier on the final output stage, a pre-driverpower amplifier (or pre-driver amp) and a pre-driver power amplifier onan initial stage and by temporally synchronizing the switching of therespective switches. The power amplifier defined with reference to FIGS.19 and 20 in the third example is used as the wide-band power amplifier(including the above-described multi-frequency matching poweramplifier). By using such a wide-band power amplifier, the inputmatching circuit and redundant switches which are required in the firstand the second examples can be eliminated, thereby obtaining asmaller-sized higher-performance switchable power amplifier.

In this example, RF signals having the following frequencies f and thefollowing output powers Pout as shown in the following table aretransmitted.

Communica- f Pout tion type Mode 1 f1 1.5 GHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.9 GHz Pout2 22 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

FIG. 28 is a configuration diagram of the fifth example of theswitchable power amplifier according to the present invention. A firstsingle-pole-dual-throw switch SW1, a first output matching circuit PC1for Mode 1 and a second power amplifier PA2 for Mode 2 are connected tothe output side of a first power amplifier PA1. The first poweramplifier PA1 includes: a first GaAs MESFET PA101; a first inter-stagematching circuit PA104; a second GaAs MESFET PA102; a second interstagematching circuit PA105; and a third GaAs MESFET PA103. The second poweramplifier PA2 includes: a fourth GaAs MESFET PA201; a third inter-stagematching circuit PA202; and a second output matching circuit PA203.

The first, second and third GaAs MESFETs PA101, PA102 and PA103 of thefirst power amplifier PA1 and the fourth GaAs MESFET PA201 of the secondpower amplifier PA2 are of a depletion type and have gate widths (Wg) of0.6 mm, 2.0 mm, 6.0 mm and 30 mm, respectively.

The first GaAs MESFET PA101, the first interstage matching circuitPA104, the second GaAs MESFET PA102 and the second inter-stage matchingcircuit PA105 among the components of the first power amplifier PA1 andthe first single-pole-dual-throw switch SW1 are integrated on a GaAssubstrate (thereby forming a first switch-integrated power amplifierSWPA1). The components of the second power amplifier PA2 or the fourthGaAs MESFETs PA201, the third inter-stage matching circuit PA202 and thesecond output matching circuit PA203 are integrated on a GaAs substrate(thereby forming a first integrated power amplifier MMPA1) and thensealed within a resin-molded package. The fourth GaAs MESFET PA201having Wg of 30 mm is mounted in a ceramic package (mounted on a ceramiccarrier and then sealed with a resin).

An integrated circuit including a GaAs MESFET is used as the firstsingle-pole-dual-throw switch SW1 (as to an exemplary circuitconfiguration, see FIG. 15 in the second example).

The operating power supply voltages of the first, second, third andfourth GaAs MESFETs PA101, PA102, PA103 and PA201 are as follows.Specifically, the drain voltages thereof are about 3.5 V and the gatevoltages thereof are negative voltages in the range from about −2.0 V toabout −3.0 V. The first and the second GaAs MESFETs PA101 and PA102 areoperated while paying much respect to the gain thereof and the third andthe fourth GaAs MESFETs PA103 and PA201 are operated in a class AB (withan idle current corresponding to about 10% of Idss) while paying muchrespect to the linearity of the input/output characteristics and thedigital distortion characteristics thereof. The GaAs MESFETs PA101,PA102, PA103 and PA201 have Idss of about 160 mA, 550 mA, 1.3 A and 7.0A, respectively.

On the other hand, the first single-pole-dual-throw switch SW1 isoperated while applying control voltages of 0 V and −4.7 V thereto.

In the switchable power amplifier of this example, by using wide-bandpower amplifiers as the first and the second power amplifiers PA1 andPA2, an input matching circuit and a switch for switching the inputmatching circuit which is required in the first and the second examplescan be eliminated.

In general, the four types of methods shown in FIGS. 22(a) to 22(d) inthe third example are used for realizing a wide-band operation of such apower amplifier. In this example, the method shown in FIG. 22(a) inwhich a negative feedback circuit or a serial circuit including aresistance and a capacitor is inserted to between the input and theoutput of the GaAs MESFET is used.

The resistance and the capacitor of the negative feedback circuit ofeach of the first and the second GaAs MESFETs PA101 and PA102 areintegrated with the first switch-integrated power amplifier SWPA1 andthen sealed within a resin-molded package. On the other hand, theresistance and the capacitor of the negative feedback circuit 101 of thethird GaAs MESFET PA103 are implemented as external circuits by usingchip components.

In determining the parameters of the matching circuits, those of thethird inter-stage matching circuits PA202 are determined such that theoutput impedance of the third GaAs MESFET PA103 is matched with theinput impedance of the fourth GaAs MESFETs PA201 at the frequency f2.

The first and the second inter-stage matching circuit PA104 and PA105within the first switch-integrated power amplifier SWPA1 are implementedby coupling capacitors so as to perform an RF coupling on the respectivestages (or to block the DC components). The first and the secondinter-stage matching circuits PA104 and PA105 may also be passivecircuits including lumped constant elements.

In conformity with the implementations of the matching circuitsdescribed in the first example, the parameters of the first and thesecond output matching circuits PC1 and PA203 are determined. As aresult, the distortion characteristics required for the π/4 shift DQPSKmodulation type in this example are satisfied.

In each of the matching circuits, the equivalent circuit thereof isrepresented by a combination of lumped constant element components. Eachof the first and the second inter-stage matching circuits PA104 andPA105 is formed by a combination of a microstrip line, a spiralinductor, an MIM (metal-insulator-metal) capacitor, a comb capacitor, athin-film resistance (such as NiCr) and the like on a GaAs substrate.

The first and the second output matching circuits PC1 and PA203 and thethird inter-stage matching circuit PA202 are formed by using variouschip components such as a chip inductor, a chip capacitor and a chipresistor.

FIG. 29 is a configuration diagram of the switchable power amplifier inthe fifth example. The respective components of the above-describedswitchable power amplifier 102 of this example, the drain voltage/gatevoltage supply section 103 for the first and the second GaAs MESFETsPA101 and PA102, the drain voltage/gate voltage supply sections 104 and105 for the third and the fourth GaAs MESFETs PA103 and PA201 and thecontrol voltage supply section 106 for the first single-pole-dual-throwswitch Swl are mounted on a printed circuit board 107.

Vdd1/Vgg1 denote the drain voltage/gate voltage to be supplied to thefirst and the second GaAs MESFETs PA101 and PA102. Vdd2/Vgg2 andVdd3/Vgg3 denote the drain voltages/gate voltages to be supplied to thethird and the fourth GaAs MESFETs PA103 and PA201, respectively. VC1denotes the control voltage to be supplied to the firstsingle-pole-dual-throw switch SW1.

The power supply controls of the drain voltage/gate voltage supplysections (or power supply controllers) 103, 104 and 105 are performed inassociation with that of the control voltage supply section (or feeder)106 for the first single-pole-dual-throw switch SW1. For example, whenPout1 is selected as the output, the feeder is controlled such that SW1selects Pout1. The drain voltage/gate voltage supply section 105 iscontrolled such that the unused PA201 is deactivated for reducing thepower consumption.

The drain voltage/gate voltage supply section is implemented by a chipinductor as a choke and a bypass capacitor or by a microstrip line formounting a switchable power amplifier on a printed circuit board and abypass capacitor.

It is noted that, when the output powers defined in Modes 1 and 2 aredifferent as in this example or when the transmission/receptionconditions of the RF signals are variable, it is necessary to vary orstabilize the output powers. Thus, since a gain control function forstabilizing an output power and holding a constant power isindispensable as a function of a transmission power amplifier, anattenuator or a power amplifier having an auto gain control (AGC) or anauto level control (ALC) function is integrated into the poweramplifier, thereby feedbacking and controlling the monitored outputpower. The output power can be monitored by a capacitance coupling or adirectional coupler (as to exemplary configurations, see FIGS. 5 and 6in the first example).

By integrating the RF section 120, the IF signal processing section 121and the base band section 122, which are shown in the block diagram ofan information communication unit in FIG. 7 in the first example, on atleast one printed circuit board (e.g., a dielectric substrate or thelike) so as to include the switchable power amplifier 102 of thisexample and collectively mounting them into the case of an informationcommunication unit, the unit can be downsized at lower costs as comparedwith a conventional example. As a result, a highly value-addedinformation communication terminal unit commonly applicable to systemshaving different frequency bands, transmission output powers andmodulation types can be obtained.

As specific exemplary implementations of the information communicationunit, the implementations shown in FIGS. 8 to 10 in the first example(i.e, an implementation in which switches for switchingtransmission/reception for Modes 1 and 2 are connected to the switchablepower amplifier and an implementation in which switches for performingdiversity transmission/reception is connected thereto) are usable. Byutilizing these implementations, the transmission and reception can beperformed with respect to Modes 1 and 2.

Alternatively, as shown in FIG. 11 in the first example, by commonlyusing a single antenna section in Modes 1 and 2 and connecting theswitch for switching the output powers of the switchable power amplifierfor Modes 1 and 2 to the switch for switching transmission andreception, the transmission and reception can also be performed withrespect to Modes 1 and 2.

It is noted that the switchable power amplifier of this example may alsobe implemented under the following specific configurations. Thefollowing MMIC implementations described in (302) to (305) arerepresentative practical ones in respects of the costs, the productionyield of a chip and the like. However, the implementations are notlimited thereto, but include the exemplary configurations and mountingmethods of hybrid ICs and MMICs as described in the first example. FIGS.30(a) to 30(c) are diagrams showing parts to be implemented as MMICs inthe fifth example. The following descriptions (302) to (305) correspondto the reference numerals attached to the broken line portions shown inFIG. 30.

(301): Implement GaAs MESFETs, a switch, matching circuits and otherperipheral circuits as hybrid ICs. The GaAs MESFETs having Wg of 0.6 mm,2 mm and 6 mm are sealed within resin-molded packages, while the GaAsMESFET having Wg of 30 mm is mounted in a ceramic package (i.e., mountedon a ceramic carrier and then sealed with a resin). Various chipcomponents such as a chip inductor, a chip capacitor and a chip resistorare used as the matching circuits and the negative feedback circuit.

(302): Integrate the first output matching circuit PC1 or the secondoutput matching circuit PA203 into the first switch-integrated poweramplifier SWPA1 and mold them with a resin.

(303): Integrate the third GaAs MESFET PA103 with the firstsingle-pole-dual-throw switch SW1 on a GaAs substrate (thereby forming asecond switch-integrated power amplifier SWPA2), integrate the firstoutput matching circuit PC1 or the second output matching circuit PA202thereto and then mold them with a resin. It is noted that the negativefeedback circuit 101 of the third GaAs MESFET PA103 may be implementedas an integrated circuit component or an external circuit component.

(304): Integrate the components of the first power amplifier PA1 with atleast one of the first output matching circuit PC1 and the second outputmatching circuit PA203 on a GaAs substrate and then mold them with aresin.

(305): Form multiple chips including a chip formed by integrating thethird GaAs MESFET PA103 with the first single-pole-dual-throw switch SW1on a GaAs substrate (the second switch-integrated power amplifier SWPA2)and a chip formed by integrating the first and the second GaAs MESFETsPA101 and PA102 and the first and the second inter-stage matchingcircuits PA104 and PA105 on a GaAs substrate (the first integrated poweramplifier MMPA1). Mounting is performed by introducing the multiplechips into a package or connecting the multiple chips onto a printedcircuit board in a bare chip manner.

In these implementations (302), (303), (304) and (305), a chipimplemented as an MMIC has been sealed within a resin-molded package ormounted in a bare chip manner, and each of the matching circuitsincluded within an MMIC includes a combination of a microstrip line, aspiral inductor, an MIM (metal-insulator-metal) capacitor, a combcapacitor, a thin-film resistance (such as NiCr) and the like on a GaAssubstrate. On the other hand, the components not included within theMMIC are individually mounted on a printed circuit board.

It is noted that an MMIC implementation includes implementing the firstor the second power amplifier PA1 or PA2 as an MMIC and selectivelyimplementing the components of each power amplifier (active elements,passive circuits and the like) as an MMIC (e.g., implementing all thecomponents of the second power amplifier PA2 other than the outputmatching circuit thereof as an MMIC).

It is also noted that not only the GaAs MESFETs used as the activeelements for the above-described power amplifier but also other activeelements such as enhanced GaAs MESFETs and transistors (e.g., MOSFETs,HBTs, HEMTs, etc.) formed on another semiconductor substrate may beused.

Moreover, a portable unit is currently supposed to satisfy theoperational requirements about an operating voltage of 3.0 V to 3.4 Vcorresponding to that of three NiCd cells or a single Li ion cell.Though the operating power supply voltage of the GaAs MESFET of thisexample is 3.5 V, the operating voltage of any other logic IC may beused. Alternatively, depending upon the type of an informationcommunication unit in question, the power supply voltage may be set atother values. If optimum active elements operating within the definedvoltage range are used, the present example may be implemented at anoperating voltage other than 3.5 V.

Furthermore, in this example, a negative voltage generated by a DC-DCconverter is used as the gate voltage of the GaAs MESFET. The presentexample may also be implemented by selecting active elements operatingby a single positive power supply so as to eliminate a negative powersupply.

The second power amplifier PA2 in this example is a single-stageamplifier. Alternatively, a multi-stage amplifier like the first poweramplifier PA1 may also be used instead.

In this example, matching circuits used as passive circuit components ofa power amplifier have been particularly described. Applicable matchingcircuits are not limited to passive components having a matchingfunction, but include various kinds of passive circuits such as a chokeinductor on a power supply line, a bypass capacitor, divided resistancesfor applying a bias, a filter, a harmonic trap circuit and anattenuator. For example, a choke inductor on a power supply line, abypass capacitor and divided resistances for applying a bias may beincluded within a power amplifier implemented as an MMIC. As for afilter, if the transmission frequency and the reception frequency of anRF signal are different from each other, a band-pass filter having apredetermined pass band width may be inserted subsequent to an outputmatching circuit or a harmonic trap circuit may be inserted into theoutput matching circuit.

In this example, RF signals corresponding to two types are transmittedby using a single-pole-dual-throw switch. However, a desired poweramplifier and a desired information communication unit may be formedeven by the use of a single-pole-multi-throw switch having multiple(three or more) throw terminals, a multi-pole-dual-throw switch havingmultiple (two or more) pole terminals or a multi-pole-multi-throw switchcollectively as the selecting switch.

The power amplifier of this example can be implemented not only underthe above-described specifications but also under the followingspecifications.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.9 GHz Pout2 22 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

Communica- f Pout tion type Mode 1 f1 1.9 GHz Pout1 22 dBm DigitalModulation Mode 2 f2 900 MHz Pout2 31 dBm Analog Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: FM modulation type

In the latter specifications, in the analog FM modulation type in Mode2, a nonlinear saturation power amplifier may also be used as a poweramplifier and matching is performed with respect to the second outputmatching circuit PA203 such that a high power added efficiency and ahigh harmonics suppression ratio are obtained at the defined outputpower of 31 dBm. On the other hand, matching is performed with respectto the first output matching circuit PC1 such that an adjacent channelleakage power is suppressed to minimal levels and a high power addedefficiency can be attained at the defined output power of 22 dBm.

EXAMPLE 6

FIGS. 31 to 34 are diagrams illustrating the sixth example of theswitchable power amplifier according to the present invention. Thisswitchable power amplifier has a function of transmitting RF signalshaving two different frequencies and two different output powers byusing wide-band power amplifiers as a driver power amplifier (or driveramp) of the power amplifier on the final output stage, a pre-driverpower amplifier (or pre-driver amp) and a pre-driver power amplifier onan initial stage and by temporally synchronizing the switching of therespective switches. The power amplifier defined with reference to FIGS.19 and 20 in the third example is used as the wide-band power amplifier(including the above-described multi-frequency matching poweramplifier). By using such a wide-band power amplifier, the inputmatching circuits and redundant switches which are required in the firstand the second examples can be eliminated, thereby obtaining asmaller-sized higher-performance switchable power amplifier.

In the sixth example, RF signals having the following frequencies f andthe following output powers Pout as shown in the following table aretransmitted.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm DigitalModulation Mode 2 f2 1.5 GHz Pout2 31 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: π/4 shift DQPSK modulation type

FIG. 31 is a configuration diagram of the sixth example of theswitchable power amplifier according to the present invention. A firstsingle-pole-dual-throw switch SW1, a first passive circuit PC1 for Mode1 and a second passive circuit PC2 for Mode 2 are connected to theoutput side of a first power amplifier PA1. The first power amplifierPA1 includes: a first GaAs MESFET PA101; a first inter-stage matchingcircuit PA104; a second GaAs MESFET PA102; a second inter-stage matchingcircuit PA105; and a third GaAs MESFET PA103. The first passive circuitPC1 includes a first output matching circuit PC101 and a first filterPC102. The second passive circuit PC2 includes a second output matchingcircuit PC201 and a second filter PC202.

The first, second and third GaAs MESFETs PA101, PA102 and PA103 as thecomponents of the first power amplifier PA1 are of a depletion type andhave gate widths (Wg) of 1 mm, 6 mm and 30 mm, respectively.

The first GaAs MESFET PA101 and the first inter-stage matching circuitPA104 among the components of the first power amplifier PA1 and thefirst single-pole-dual-throw switch SW1 are integrated on a GaAssubstrate (thereby forming a first switch-integrated power amplifierSWPA1) and then sealed within a resin-molded package. The second GaAsMESFET PA102 having Wg of 6 mm is mounted within a resin-molded packageand the third GaAs MESFET PA103 having Wg of 30 mm is mounted in aceramic package (mounted on a ceramic carrier and then sealed with aresin).

An integrated circuit including a GaAs MESFET is used as the firstsingle-pole-dual-throw switch SW1 (as to an exemplary circuitconfiguration, see FIG. 15 in the second example).

The operating power supply voltages of the first, second and third GaAsMESFETs PA101, PA102 and PA103 are as follows. Specifically, the drainvoltages thereof are 3.5 V and the gate voltages thereof are negativevoltages in the range from −2.0 V to −3.0 V. The first GaAs MESFET PA101is operated while paying much respect to the gain thereof and the secondand the third GaAs MESFETs PA102 and PA103 are operated in a class AB(with an idle current corresponding to about 10% of Idss) while payingmuch respect to the linearity of the input/output characteristics andthe digital distortion characteristics thereof. The GaAs MESFETs PA101,PA102 and PA103 have Idss of about 250 mA, about 1.3 A and about 7.0 A,respectively.

On the other hand, the first single-pole-dual-throw switch SW1 isoperated while applying control voltages of 0 V and −4.7 V thereto. Inthe switchable power amplifier of this example, by using a wide-bandpower amplifier as the first power amplifier PA1, an input matchingcircuit and a switch for switching the input matching circuit which isrequired in the first and the second examples can be eliminated.

In general, the four types of methods shown in FIGS. 22(a) to 22(d) inthe third example are used for realizing a wide-band operation of such apower amplifier. In this example, the method shown in FIG. 22(a) inwhich a negative feedback circuit implemented as a serial circuitincluding a resistance and a capacitor is inserted to between the inputand the output of the GaAs MESFET is used.

The resistance and the capacitor of the negative feedback circuit of thefirst GaAs MESFETs PA101 are integrated with the first switch-integratedpower amplifier SWPA1 and then sealed within a resin-molded package. Onthe other hand, the resistance and the capacitor of the first negativefeedback circuit 101 of the second GaAs MESFET PA102 are formed asexternal circuits by using chip components. As for the third GaAs MESFETPA103, a second negative feedback circuit is integrated therewith orimplemented as an external circuit or as an impedance converter enablinga wide-band matching (i.e., matching the output impedances of the secondGaAs MESFET PA102 with the input impedances of the third GaAs MESFETPA103 at the frequencies f1 and f2 or in a frequency band including f1and f2) is used therefor.

In determining the parameters of the matching circuits, those of thethird inter-stage matching circuits PA202 are determined such that theoutput impedance of the third GaAs MESFET PA103 is matched with theinput impedance of the fourth GaAs MESFETs PA201 at the frequency f2.

The first inter-stage matching circuit PA104 is implemented by couplingcapacitors so as to perform an RF coupling on the respective stages (orto block the DC components). The first and the second inter-stagematching circuits PA104 and PA105 may also be passive circuits includinglumped constant elements.

In conformity with the implementations of the matching circuitsdescribed in the first example, the parameters of the first and thesecond output matching circuits PC101 and PC201 are determined. As aresult, the distortion characteristics required for the π/4 shift DQPSKmodulation type in this example are satisfied.

In each of the matching circuits, the equivalent circuit thereof isrepresented by a combination of lumped constant element components. Whenthe first and the second inter-stage matching circuits PA104 and PA105and the first and the second output matching circuits PC101 and PC201are integrated on a GaAs substrate or the like, each of the matchingcircuits is formed by a combination of a microstrip line, a spiralinductor, an MIM (metal-insulator-metal) capacitor, a comb capacitor, athin-film resistance (such as NiCr) and the like on a GaAs substrate.

The first and the second output matching circuits PC101 and PC201 andthe second inter-stage matching circuit PA105 are formed by usingvarious chip components such as a chip inductor, a chip capacitor and achip resistor.

Each of the first and the second filters PC102 and PC202 is implementedas a band pass filter having a predetermined pass band width withrespect to the frequencies f1 and f2 or as a combination of such a bandpass filter and a low pass filter or a high pass filter including f1 andf2 in the pass band thereof. In general, a dielectric filter as a chipcomponent, a surface acoustic wave filter (SAW filter) or the like isused as a filter.

FIG. 32 is a configuration diagram of the switchable power amplifier inthe sixth example. The respective components of the above-describedswitchable power amplifier 103 of this example, the drain voltage/gatevoltage supply section 104 for the first GaAs MESFET PA101, the drainvoltage/gate voltage supply section 105 for the second and the thirdGaAs MESFETs PA102 and PA103 and the control voltage supply section 106for the first single-pole-dual-throw switch SW1 are mounted on a printedcircuit board 107.

Vdd1/Vgg1 denote the drain voltage/gate voltage to be supplied to thefirst GaAs MESFETs PA101. Vdd2/Vgg2 denote the drain voltage/gatevoltage to be supplied to the second and the third GaAs MESFETs PA102and PA103. VC1 denotes the control voltage to be supplied to the firstsingle-pole-dual-throw switch SW1.

The power supply controls of the drain voltage/gate voltage supplysections (or power supply controllers) 104 and 105 are performed inassociation with that of the control voltage supply section (or feeders)106 for the first single-pole-dual-throw switch SW1. For example, whenPout1 is selected as the output, the feeder is controlled such that SW1selects Pout1.

The drain voltage/gate voltage supply section is implemented by a chipinductor as a choke and a bypass capacitor or by a microstrip line formounting a switchable power amplifier on a printed circuit board and abypass capacitor.

By integrating the RF section 120, the IF signal processing section 121and the base band section 122, which are shown in the block diagram ofan information communication unit in FIG. 7 in the first example, on atleast one printed circuit board (e.g., a dielectric substrate or thelike) so as to include the switchable power amplifier 103 of thisexample and collectively mounting them into the case of an informationcommunication unit, the unit can be downsized at lower costs as comparedwith a conventional example. As a result, a highly value-addedinformation communication terminal unit commonly applicable to systemshaving different frequency bands, transmission output powers andmodulation types can be obtained.

As specific exemplary implementations of the information communicationunit, the implementations shown in FIGS. 8 to 10 in the first example(i.e, an implementation in which switches for switchingtransmission/reception for Modes 1 and 2 are connected to the switchablepower amplifier and an implementation in which switches for performingdiversity transmission/reception is connected thereto) are usable. Byutilizing these implementations, the transmission and reception can beperformed with respect to Modes 1 and 2.

Alternatively, as shown in FIG. 11 in the first example, by commonlyusing a single antenna section in Modes 1 and 2 and connecting theswitch for switching the output powers of the switchable power amplifierfor Modes 1 and 2 to the switch for switching transmission andreception, the transmission and reception can also be performed withrespect to Modes 1 and 2.

It is noted that the switchable power amplifier of this example may alsobe implemented under the following specific configurations. (1) and (2)are practical in respects of the costs, the production yield of a chipand the like. As for (3), (4) and (5), the third GaAs MESFET PA103having Wg of 30 mm is preferably mounted in a ceramic package in view ofthe thermal environment during the actual operation thereof, and thus isnot suitable for being integrated with the other chips. Nevertheless,such a case will also be presented as an exemplary implementation.Furthermore, the exemplary configurations and mounting methods of hybridICs as described in the first example may also be used. FIG. 33 is adiagram showing a part to be implemented as an MMIC in the sixth exampleand corresponding to the description (2). In FIG. 33, the broken linesindicate a portion to be implemented as an MMIC.

(1): Implement GaAs MESFETs, a switch, matching circuits and otherperipheral circuits as hybrid ICs. The GaAs MESFETs having Wg of 1 mmand 6 mm are sealed within resin-molded packages, while the GaAs MESFEThaving Wg of 30 mm is mounted in a ceramic package (i.e., mounted on aceramic carrier and then sealed with a resin). Various chip componentssuch as a chip inductor, a chip capacitor and a chip resistor are usedas the matching circuits and the negative feedback circuit. A dielectricfilter as a chip component, a surface acoustic wave filter (SAW filter)or the like is used as the filter.

(2): Integrate the first output matching circuit PC101 or the secondoutput matching circuit PC201 into the first switch-integrated poweramplifier SWPA1 and mold them with a resin.

(3): Integrate the third GaAs MESFET PA103 and the firstsingle-pole-dual-throw switch SW1 on a GaAs substrate (thereby forming asecond switch-integrated power amplifier SWPA2), integrate the firstoutput matching circuit PC101 or the second output matching circuitPC201 thereto and then mold them with a resin. It is noted that thenegative feedback circuit 101 of the third GaAs MESFET PA103 may beformed as an integrated circuit component or an external circuitcomponent.

(4): Integrate the components of the first power amplifier PA1 with atleast one of the first output matching circuit PC101 and the secondoutput matching circuit PC201 on a GaAs substrate and then mold themwith a resin.

(5): Form multiple chips including a chip formed by integrating thethird GaAs MESFET PA103 and the first single-pole-dual-throw switch SW1on a GaAs substrate (the second switch-integrated power amplifier SWPA2)and a chip formed by integrating the first and the second GaAs MESFETsPA101 and PA102 with the first and the second inter-stage matchingcircuits PA104 and PA105 on a GaAs substrate (the first integrated poweramplifier MMPA1). Mounting is performed by introducing the multiplechips into a package or connecting the multiple chips onto a printedcircuit board in a bare chip manner.

In the descriptions (2) to (5), a chip implemented as an MMIC has beensealed within a resin-molded package or mounted in a bare chip manner,and a matching circuit included within the MMIC includes a combinationof a microstrip line, a spiral inductor, an MIM (metal-insulator-metal)capacitor, a comb capacitor, a thin-film resistance (such as NiCr) andthe like on a GaAs substrate. On the other hand, the components notincluded within the MMIC are individually mounted on a printed circuitboard.

It is noted that an MMIC implementation includes implementing the firstpower amplifier PA1 as an MMIC and selectively implementing thecomponents of the power amplifier (active elements, passive circuits andthe like) as an MMIC (e.g., implementing all the components of the firstpower amplifier PA1 other than the output matching circuit thereof as anMMIC).

It is also noted that not only the GaAs MESFETs used as the activeelements for the above-described power amplifier but also other activeelements such as enhanced GaAs MESFETs and transistors (e.g., MOSFETs,HBTs, HEMTs, etc.) formed on another semiconductor substrate may beused.

Moreover, a portable unit is currently supposed to satisfy theoperational requirements about an operating voltage of 3.0 V to 3.4 Vcorresponding to that of three NiCd cells or a single Li ion cell.Though the operating power supply voltage of the GaAs MESFET of thisexample is 3.5 V, the operating voltage of any other logic IC may beused. Alternatively, depending upon the type of an informationcommunication unit in question, the power supply voltage may be set atother values. If optimum active elements operating within the definedvoltage range are used, the present example may be implemented at anoperating voltage other than 3.5 V.

Furthermore, in this example, a negative voltage generated by a DC-DCconverter is used as the gate voltage of the GaAs MESFET. The presentexample may also be implemented by selecting active elements operatingby a single positive power supply so as to eliminate a negative powersupply.

In this example, matching circuits used as passive circuit components ofa power amplifier have been particularly described. Applicable matchingcircuits are not limited to passive components having a matchingfunction, but include various kinds of passive circuits such as a chokeinductor on a power supply line, a bypass capacitor, divided resistancesfor applying a bias, a filter, a harmonic trap circuit and anattenuator. For example, a choke inductor on a power supply line, abypass capacitor and divided resistances for applying a bias may beincluded within a power amplifier implemented as an MMIC. As for afilter, if the transmission frequency and the reception frequency of anRF signal are different from each other, a band-pass filter having apredetermined pass band width may be inserted subsequent to an outputmatching circuit or a harmonic trap circuit may be inserted into theoutput matching circuit.

In this example, RF signals corresponding to two types are transmittedby using a single-pole-dual-throw switch. However, a desired poweramplifier and a desired information communication unit may be formedeven by the use of a single-pole-multi-throw switch having multiple(three or more) throw terminals, a multi-pole-dual-throw switch havingmultiple (two or more) pole terminals or a multi-pole-multi-throw switchcollectively as the selecting switch.

The power amplifier of this example can be implemented not only underthe above-described specifications but also under the followingspecifications.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm AnalogModulation Mode 2 f2 1.5 GHz Pout2 31 dBm Digital Modulation Mode 1: FMmodulation type Mode 2: π/4 shift DQPSK modulation type

In the analog FM modulation type in Mode 1, a nonlinear saturation poweramplifier may also be used as a power amplifier and matching isperformed with respect to the first output matching circuit PC101 suchthat a high power added efficiency and a high harmonics suppressionratio are obtained at the defined output power of 31 dBm. On the otherhand, matching is performed with respect to the second output matchingcircuit PC201 such that an adjacent channel leakage power is suppressedto minimal levels and a high power added efficiency can be attained atthe defined output power of 22 dBm.

Though this example uses the specifications in which the output powersare equal, the present example is also applicable to a case where thedefined output powers are different in Modes 1 and 2 shown in thefollowing table by providing a gain control function such as those shownin FIGS. 5 and 6 in the first example.

Communica- f Pout tion type Mode 1 f1 900 MHz Pout1 31 dBm AnalogModulation Mode 2 f2 2.4 GHz Pout2 26 dBm Digital Modulation Mode 1: π/4shift DQPSK modulation type Mode 2: spread spectrum (SS) QPSK modulationtype

FIG. 34 is a configuration diagram in which a secondsingle-pole-dual-throw switch SW2 is connected to the respective outputterminals of the first passive circuit PC1 and the second passivecircuit PC2 connected to the dual-throw terminals of the firstsingle-pole-dual-throw switch SW1 in the power amplifier shown in FIG.31. By switching the second single-pole-dual-throw switch SW2 insynchronization with the first single-pole-dual-throw switch SW1, twotypes of RF signals can be transmitted. That is to say, the connectionto an antenna is realized either under the configuration shown in FIG.21 in which the outputs of the first passive circuit PC1 and the secondpassive circuit PC2 connected to the dual-throw terminals of the firstsingle-pole-dual-throw switch SW1 reach respective antennas via anantenna duplexer or a switch or under the configuration shown in FIG. 34in which the outputs reach a single antenna via an antenna duplexer, aswitch or the like. In this example, other components such as a filtermay be interposed into the path extending to the antenna.

It is noted that the configuration shown in FIG. 34 is similarlyapplicable to the first to the fifth examples, too.

Furthermore, some of the configurations described in the first to thesixth examples may be combined. FIG. 39 is a block diagram of a poweramplifier and a communication unit according to the present invention.An RF signal input through an input terminal In is selectively input toone of the input matching circuits PC1 and PC2 via a switch SW1. Eitherthe output of PC1 or the output of PC2 is selected by a switch SW2 andinput to an amplifier PA1. The output of PA1 is selectively input to oneof the output matching circuits PC3 and PC4 via a switch SW3. Either theoutput of PC3 or the output of PC4 is selected by a switch SW4 and thensupplied to the terminal TX of a switch SW5. At the time oftransmission, the switch SW5 connects the terminal TX to an antenna ANT.On the other hand, at the time of reception, the switch SW5 connects aterminal RX to the antenna ANT and an input signal received through theantenna ANT is supplied to a front-end circuit FE via the switch SW5.

For example, if the switch SW5, the antenna ANT and the front-endcircuit FE are omitted from the communication unit shown in FIG. 39, aswitchable power amplifier may also be implemented.

INDUSTRIAL APPLICABILITY

As is apparent from the foregoing description, according to the presentinvention, two amplifiers for amplifying signals having differentfrequency bands are switched by a single-pole-dual-throw switch. As aresult, a power amplifier and a communication unit which can amplify RFsignals having different frequency bands can be provided.

In addition, according to the present invention, two amplifiers foramplifying signals having different output powers are switched by asingle-pole-dual-throw switch. As a result, a power amplifier and acommunication unit which can amplify RF signals having different outputpowers can be provided.

Moreover, according to the present invention, by switching a passivecircuit and an amplifier instead of the two amplifiers or by combiningsome of the above-described configurations, a power amplifier and acommunication unit which can amplify RF signals having differentfrequencies and/or different output powers can be provided.

Furthermore, according to the present invention, by providing a switchfor switching transmission and reception for the output terminal of apower amplifier, a communication unit which can receive RF signalshaving frequencies can be provided.

What is claimed is:
 1. A communication unit comprising: a firstamplifier having an input node and an output node; a second amplifierhaving an input node and an output node operable in a first mode at afirst frequency; and output matching circuit having an input node and anoutput node operable in a second mode at a second frequency; a firstswitch having a single-pole node and two or more multi-throw nodes; asecond switch having a single-pole node and two or more multi-thrownodes; and an antenna, wherein the output node of the first amplifier isconnected to the single-pole node of the first switch, at least one ofthe multi-throw nodes of the first switch is connected to the input nodeof the second amplifier and at least another multi-throw node of thefirst switch is connected to the input node of the output matchingcircuit, the output node of the second amplifier is connected to one ofthe multi-throw nodes of the second switch and the output node of theoutput matching circuit is connected to another multi-throw node of thesecond switch, the single-pole node of the second switch is connected tothe antenna whereby in synchronization with the first switch, operationin either the first mode or the second mode is provided, and the firstfrequency is different from the second frequency.
 2. A communicationunit comprising: a first amplifier having an input node and an outputnode; a second amplifier having an input node and an output nodeoperable in a first mode at a first frequency; a third amplifier havingan input node and an output node operable in a second mode at a secondfrequency; a first switch having a single-pole node and two or moremulti-throw nodes; a second switch having a single-pole node and two ormore multi-throw nodes; and an antenna, wherein the output node of thefirst amplifier is connected to the single-pole node of the firstswitch, at least one of the multi-throw nodes of the first switch isconnected to the input node of the second amplifier and at least anothermulti-throw node of the first switch is connected to the input node ofthe third amplifier, the output node of the second amplifier isconnected to one of the multi-throw nodes of the second switch and theoutput node of the third amplifier is connected to another multi-thrownode of the second switch, the single-pole node of the second switch isconnected to the antenna whereby in synchronization with the firstswitch, operation in either the first mode or the second mode isprovided, and the first frequency is different from the secondfrequency.
 3. A communication unit comprising: an amplifier having aninput node and an output node; a first output matching circuit having aninput node and an output node operable in a first mode at a firstfrequency; a second output matching circuit having an input node and anoutput node operable in a second mode at a second frequency; a firstswitch having a single-pole node and two or more multi-throw nodes; asecond switch having a single-pole node and two or more multi-thrownodes; and an antenna, wherein the output node of the amplifier isconnected to the single-pole node of the first switch, at least one ofthe multi-throw nodes of the first switch is connected to the input nodeof the first output matching circuit and at least another multi-thrownode of the first switch is connected to the input node of the secondoutput matching circuit, the output node of the first output matchingcircuit is connected to one of the multi-throw nodes of the secondswitch and the output node of the second output matching circuit isconnected to another multi-throw node of the second switch, thesingle-pole node of the second switch is connected to the antennawhereby in synchronization with the first switch, operation in eitherthe first mode or the second mode is provided, and the first frequencyis different from the second frequency.
 4. A communication unitcomprising: a first passive output matching circuit having an input nodeand an output node operable in a first mode at a first frequency; asecond passive output matching circuit having an input node and anoutput node operable in a second mode at a second frequency; a thirdpassive output matching circuit having an input node and an output node;a fourth passive output matching circuit having an input node and anoutput node; a first switch having a single-pole node and two or moremulti-throw nodes; a second switch having a single-pole node and two ormore multi-throw nodes; a third switch having a single-pole node and twoor more multi-throw nodes; a fourth switch having a single-pole node andtwo or more multi-throw nodes; an amplifier having an input node and anoutput node; and an antenna, wherein one of the multi-throw nodes of thefirst switch is connected to the input node of the first passive outputmatching circuit, another multi-throw node of the first switch isconnected to the input node of the second passive output matchingcircuit and the output node of the amplifier is connected to thesingle-pole node of the first switch, the single-pole node of the secondswitch is connected to an input, at least one of the multi-throw nodesof the second switch is connected to the input node of the third passiveoutput matching circuit and at least another multi-throw node of thesecond switch is connected to the input node of the fourth passiveoutput matching circuit, the single-pole node of the third switch isconnected to the input node of the amplifier, at least one of themulti-throw nodes of the third switch is connected to the output node ofthe third passive output matching circuit and at least anothermulti-throw node of the third switch is connected to the output node ofthe fourth passive output matching circuit, one of the multi-throw nodesof the fourth switch is connected to the output node of the firstpassive output matching circuit and another multi-throw node of thefourth switch is connected to the output node of the second passiveoutput matching circuit, the single-pole node of the fourth switch isconnected to the antenna whereby in synchronization with the firstswitch, operation in either the first mode or the second mode isprovided, and the first frequency is different from the secondfrequency.
 5. A communication unit according to claim 1, wherein anoutput power of the communication unit when operating in the first modeis the same as an output power of the communication unit when operatingin the second mode.
 6. A communication unit according to claim 2,wherein an output power of the communication unit when operating in thefirst mode is the same as an output power of the communication unit whenoperating in the second mode.
 7. A communication unit according to claim3, wherein an output power of the communication unit when operating inthe first mode is the same as an output power of the communication unitwhen operating in the second mode.
 8. A communication unit according toclaim 4, wherein an output power of the communication unit whenoperating in the first mode is the same as an output power of thecommunication unit when operating in the second mode.